Michael Hendzel
University of Alberta, Experimental Oncology, Faculty Member
DNA double-strand breaks (DSBs) are repaired mainly by non-homologous end joining or homologous recombination (HR). Cell cycle stage and DNA end resection are believed to regulate the commitment to HR repair. Here we identify RNF138 as a... more
DNA double-strand breaks (DSBs) are repaired mainly by non-homologous end joining or homologous recombination (HR). Cell cycle stage and DNA end resection are believed to regulate the commitment to HR repair. Here we identify RNF138 as a ubiquitin E3 ligase that regulates the HR pathway. RNF138 is recruited to DNA damage sites through zinc fingers that have a strong preference for DNA with 5'- or 3'-single-stranded overhangs. RNF138 stimulates DNA end resection and promotes ATR-dependent signalling and DSB repair by HR, thereby contributing to cell survival on exposure to DSB-inducing agents. Finally, we establish that RNF138-dependent Ku removal from DNA breaks is one mechanism whereby RNF138 can promote HR. These results establish RNF138 as an important regulator of DSB repair pathway choice.
Research Interests: Biology, Cell Biology, DNA damage, DNA repair, Medicine, and 15 moreBiological Sciences, DNA, RNA interference, Ubiquitin, Humans, Mutation, HeLa cells, Ubiquitin ligase, Homologous Recombination, DNA ligase, Protein Binding, single stranded DNA, Ubiquitination, Immunoblotting, and Medical and Health Sciences
Research Interests:
Research Interests:
DNA damage evokes a complex and highly coordinated DNA damage response (DDR) that is integral to the suppression of genomic instability. Double-strand breaks (DSBs) are considered the most deleterious form damage. Evidence suggests that... more
DNA damage evokes a complex and highly coordinated DNA damage response (DDR) that is integral to the suppression of genomic instability. Double-strand breaks (DSBs) are considered the most deleterious form damage. Evidence suggests that trimethylation of histone H3 lysine 9 (H3K9me3) presents a barrier to DSB repair. Also, global levels of histone methylation are clinically predictive for several tumor types. Therefore, demethylation of H3K9 may be an important step in the repair of DSBs. The KDM4 subfamily of demethylases removes H3K9 tri- and dimethylation and contributes to the regulation of cellular differentiation and proliferation; mutation or aberrant expression of KDM4 proteins has been identified in several human tumors. We hypothesize that members of the KDM4 subfamily may be components of the DDR. We found that Kdm4b-enhanced GFP (EGFP) and KDM4D-EGFP were recruited rapidly to DNA damage induced by laser micro-irradiation. Focusing on the clinically relevant Kdm4b, we found that recruitment was dependent on poly(ADP-ribose) polymerase 1 activity as well as Kdm4b demethylase activity. The Kdm4 proteins did not measurably accumulate at γ-irradiation-induced γH2AX foci. Nevertheless, increased levels of Kdm4b were associated with decreased numbers of γH2AX foci 6 h after irradiation as well as increased cell survival. Finally, we found that levels of H3K9me2 and H3K9me3 were decreased at early time points after 2 gray of γ-irradiation. Taken together, these data demonstrate that Kdm4b is a DDR protein and that overexpression of Kdm4b may contribute to the failure of anti-cancer therapy that relies on the induction of DNA damage.
Research Interests:
Research Interests:
Polycomb-repressive complex 1 (PRC1)-mediated histone ubiquitylation plays an important role in aberrant gene silencing in human cancers and is a potential target for cancer therapy. Here we show that... more
Polycomb-repressive complex 1 (PRC1)-mediated histone ubiquitylation plays an important role in aberrant gene silencing in human cancers and is a potential target for cancer therapy. Here we show that 2-pyridine-3-yl-methylene-indan-1,3-dione (PRT4165) is a potent inhibitor of PRC1-mediated H2A ubiquitylation in vivo and in vitro. The drug also inhibits the accumulation of all detectable ubiquitin at sites of DNA double-strand breaks (DSBs), the retention of several DNA damage response proteins in foci that form around DSBs, and the repair of the DSBs. In vitro E3 ubiquitin ligase activity assays revealed that PRT4165 inhibits both RNF2 and RING 1A, which are partially redundant paralogues that together account for the E3 ubiquitin ligase activity found in PRC1 complexes, but not RNF8 nor RNF168. Because ubiquitylation is completely inhibited despite the efficient recruitment of RNF8 to DSBs, our results suggest that PRC1-mediated monoubiquitylation is required for subsequent RNF8- and/or RNF168-mediated polyubiquitylation. Our results demonstrate the unique feature of PRT4165 as a novel chromatin-remodeling compound and provide a new tool for the inhibition of ubiquitylation signaling at DNA double-strand breaks.
Research Interests:
Research Interests:
Research Interests:
We have generated and characterized a novel site-specific antibody highly specific for the phosphorylated form of the amino-terminus of histone H3 (Ser10). In this study, we used this antibody to examine in detail the relationship between... more
We have generated and characterized a novel site-specific antibody highly specific for the phosphorylated form of the amino-terminus of histone H3 (Ser10). In this study, we used this antibody to examine in detail the relationship between H3 phosphorylation and mitotic chromosome condensation in mammalian cells. Our results extend previous biochemical studies by demonstrating that mitotic phosphorylation of H3 initiates nonrandomly in pericentromeric heterochromatin in late G2 interphase cells. Following initiation, H3 phosphorylation appears to spread throughout the condensing chromatin and is complete in most cell lines just prior to the formation of prophase chromosomes, in which a phosphorylated, but nonmitotic, chromosomal organization is observed. In general, there is a precise spatial and temporal correlation between H3 phosphorylation and initial stages of chromatin condensation. Dephosphorylation of H3 begins in anaphase and is complete immediately prior to detectable chromosome decondensation in telophase cells. We propose that the singular phosphorylation of the amino-terminus of histone H3 may be involved in facilitating two key functions during mitosis: (1) regulate protein-protein interactions to promote binding of trans-acting factors that "drive" chromatin condensation as cells enter M-phase and (2) coordinate chromatin decondensation associated with M-phase.
Research Interests: Genetics, Fashion design, Immunohistochemistry, Centromere Biology, International Retailing, and 17 moreProtein-Protein Interaction, Retail Management, Mitosis, Cell line, Fashion Merchandising, Animals, Temporal Correlation, Global Fashion, Phosphorylation, Histones, Apparel Industry, Fashion, Rabbits, Amino Acid Sequence, Fashion Industry, Phosphopeptides, and Heterochromatin
We have evaluated the effects of different DNA denaturation protocols commonly used in DNA fluorescent in situ hybridization (FISH) experiments on chromatin structure using indirect immunofluorescence. The use of antibodies to acetylated... more
We have evaluated the effects of different DNA denaturation protocols commonly used in DNA fluorescent in situ hybridization (FISH) experiments on chromatin structure using indirect immunofluorescence. The use of antibodies to acetylated histones H3 and H4 demonstrates that the different procedures differ considerably in their extent of histone displacement. Procedures involving paraformaldehyde fixation were found to be compatible with the structural preservation of acetylated chromatin organization by indirect immunofluorescence. These results provide a basis for interpreting DNA FISH experiments aimed at determining chromatin organization of individual loci.
Research Interests:
The study of RNA pol II-mediated transcription regulation has been dominated by molecular biological approaches. Although these methods continue to provide important insights, other approaches are required to insure against an... more
The study of RNA pol II-mediated transcription regulation has been dominated by molecular biological approaches. Although these methods continue to provide important insights, other approaches are required to insure against an oversimplified view of gene expression. Improvements in EM methods and the development of the confocal light microscope have provided alternative and complementary means of investigating gene regulation. Information on the "context" in which cis- and trans-acting factors operate can be achieved with these techniques. As a result, the spatial compartmentalization of nuclear processes involved in transcriptional and post-transcriptional processing has received considerable attention.
Research Interests:
Polycomb protein histone methyltransferase, enhancer of Zeste homolog 2 (EZH2), is frequently overexpressed in human malignancy and is implicated in cancer cell proliferation and invasion. However, it is largely unknown whether EZH2 has a... more
Polycomb protein histone methyltransferase, enhancer of Zeste homolog 2 (EZH2), is frequently overexpressed in human malignancy and is implicated in cancer cell proliferation and invasion. However, it is largely unknown whether EZH2 has a role in modulating the DNA damage response. Here, we show that polycomb repressive complex 2 (PRC2) is recruited to sites of DNA damage. This recruitment is independent of histone 2A variant X (H2AX) and the PI-3-related kinases ATM and DNA-PKcs. We establish that PARP activity is required for retaining PRC2 at sites of DNA damage. Furthermore, depletion of EZH2 in cells decreases the efficiency of DSB repair and increases sensitivity of cells to gamma-irradiation. These data unravel a crucial role of PRC2 in determining cancer cellular sensitivity following DNA damage and suggest that therapeutic targeting of EZH2 activity might serve as a strategy for improving conventional chemotherapy in a given malignancy.
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
The Notch signaling pathway is essential for embryonic development, organogenesis, and tissue homeostasis. Aberrant Notch signaling is associated with several types of cancers. The active form of Notch receptor is its intracellular domain... more
The Notch signaling pathway is essential for embryonic development, organogenesis, and tissue homeostasis. Aberrant Notch signaling is associated with several types of cancers. The active form of Notch receptor is its intracellular domain (NICD), which is released from the cell membrane by serial proteolytic cleavages following ligand binding. Dose-dependent effects of NICD on cellular phenotypes have been observed under several conditions although the underlying mechanisms have not been well studied. Moreover, there are four mammalian Notch paralogs that have redundant as well as unique functions. The molecular basis for this variability is also not well understood. In this study, we used size exclusion chromatography to examine the overall distribution of NICD among NICD-containing protein complexes under conditions of increasing NICD abundance. We found that the assembly of NICD protein complexes was dose-dependent and that the abundance of the canonical complex was limited by, MAML, one of the proteins involved in the formation of canonical NICD transactivation complex, which became saturated with increasing NICD abundance. In addition, N4ICD showed a unique elution profile among the four NICDs. These results help to explain the dose-dependent and paralog-specific activities of NICD. These results are informative for the development of new reagents to block Notch signaling for therapeutic benefit.
Research Interests:
Research Interests: Kinetics, Medical Microbiology, Fluorescence Microscopy, Radiobiology of Ionizing Radiation, DNA damage, and 19 moreWestern blotting, Biological Sciences, DNA, Humans, Diffusion, Physical sciences, Sodium Dodecyl Sulfate-Polyacrylamide Gel Electrophoresis, Enzyme, Subcellular Localization, Neuroblastoma, Cell nucleus, Isoenzymes, DNA damage response, fluorescence recovery after photobleaching (FRAP), Subcellular Fractions, Fusion Protein, Cytoplasm, Frap, and Biochemistry and cell biology
Research Interests:
<p>The vertical axis represents the log of the excess odds ratio over randomness, with a value of zero equivalent to random association. The different nuclear body components are labeled as in <a... more
<p>The vertical axis represents the log of the excess odds ratio over randomness, with a value of zero equivalent to random association. The different nuclear body components are labeled as in <a href="http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.0020139#pcbi-0020139-g003" target="_blank">Figure 3</a>. NCBP “association” to CBP is labeled 01, with CBP “association” to NCBP labeled 10. The bars represent a 95% confidence interval for the mean association (see text for further details). Note the significant difference in “probability of association” between K5 and K12.</p
Research Interests:
Research Interests:
Research Interests:
Research Interests:
The incorporation of newly synthesized histones among various chromatin fraction isolated from non-replicating cell-cycle-phase-Go chicken immature erythrocytes was investigated. We find that newly synthesized erythroid-specific histone... more
The incorporation of newly synthesized histones among various chromatin fraction isolated from non-replicating cell-cycle-phase-Go chicken immature erythrocytes was investigated. We find that newly synthesized erythroid-specific histone Hl variant H5, is incorporated randomly into chromatin. In contrast, newly synthesized nucleosomal histones H2A, H2A.Z, H2B, H3.3, and H4 are preferentially found in a fraction that is highly enriched in active/competent gene chromatin fragments and depleted in repressed gene chromatin. Moreover, ubiquitinated species of histones H2A and H2B and hyperacetylated species of H4 and H2B, which are complexed to active DNA, are labelled. These observations provide evidence that newly synthesized histones preferentially exchange with the nucleosomal histones of transcriptionally active/component chromatin domains. The results of this study suggest that nucleosomes of active chromatin may be inherently less stable than bulk nucleosomes in vivo and have impli...
Research Interests: Chromatography, Biology, Medicine, Biological Sciences, Animals, and 15 moreCell Fractionation, Biochemical, Sodium Dodecyl Sulfate-Polyacrylamide Gel Electrophoresis, Solubility, Nucleosomes, Chromatin, CHEMICAL SCIENCES, Histones, Chickens, Acetylation, Hydroxyapatites, Durapatite, Erythrocytes, Sodium Chloride, and Medical and Health Sciences
Research Interests:
Research Interests:
In the current model of DNA SSBR, PARP1 is regarded as the sensor of single-strand breaks (SSBs). However, biochemical studies have implicated LIG3 as another possible SSB sensor. Using a laser micro-irradiation protocol that... more
In the current model of DNA SSBR, PARP1 is regarded as the sensor of single-strand breaks (SSBs). However, biochemical studies have implicated LIG3 as another possible SSB sensor. Using a laser micro-irradiation protocol that predominantly generates SSBs, we were able to demonstrate that PARP1 is dispensable for the accumulation of different single-strand break repair (SSBR) proteins at sites of DNA damage in live cells. Furthermore, we show in live cells for the first time that LIG3 plays a role in mediating the accumulation of the SSBR proteins XRCC1 and PNKP at sites of DNA damage. Importantly, the accumulation of LIG3 at sites of DNA damage did not require the BRCT domain-mediated interaction with XRCC1. We were able to show that the N-terminal ZnF domain of LIG3 plays a key role in the enzyme's SSB sensing function. Finally, we provide cellular evidence that LIG3 and not PARP1 acts as the sensor for DNA damage caused by the topoisomerase I inhibitor, irinotecan. Our results...
Research Interests:
Polycomb group (PcG) proteins are major determinants of cell identity, stem cell pluripotency, and epigenetic gene silencing during development. The polycomb repressive complex 1, which contains BMI1, RING1, and RING2, functions as an... more
Polycomb group (PcG) proteins are major determinants of cell identity, stem cell pluripotency, and epigenetic gene silencing during development. The polycomb repressive complex 1, which contains BMI1, RING1, and RING2, functions as an E3-ubuiquitin ligase. We found that BMI1 and RING2 are recruited to sites of DNA double-strand breaks (DSBs) where they contribute to the ubiquitylation of γ-H2AX. In the absence of BMI1, several proteins dependent on ubiquitin signaling, including 53BP1, BRCA1, and RAP80, are impaired in recruitment to DSBs. Loss of BMI1 sensitizes cells to ionizing radiation to the same extent as loss of RNF8. The simultaneous depletion of both proteins revealed an additive increase in radiation sensitivity. These data uncover an unexpected link between the polycomb and the DNA damage response pathways, and suggest a novel function for BMI1 in maintaining genomic stability.
Research Interests:
Background Poly(ADP-ribose) polymerases (PARPs) catalyze the formation of poly(ADP-ribose) (pADPr), a post-translational modification involved in several important biological processes, namely surveillance of genome integrity, cell cycle... more
Background Poly(ADP-ribose) polymerases (PARPs) catalyze the formation of poly(ADP-ribose) (pADPr), a post-translational modification involved in several important biological processes, namely surveillance of genome integrity, cell cycle progression, initiation of the DNA damage response, apoptosis, and regulation of transcription. Poly(ADP-ribose) glycohydrolase (PARG), on the other hand, catabolizes pADPr and thereby accounts for the transient nature of poly(ADP-ribosyl)ation. Our investigation of the interactomes of PARP-1, PARP-2, and PARG by affinity-purification mass spectrometry (AP-MS) aimed, on the one hand, to confirm current knowledge on these interactomes and, on the other hand, to discover new protein partners which could offer insights into PARPs and PARG functions. Results PARP-1, PARP-2, and PARG were immunoprecipitated from human cells, and pulled-down proteins were separated by gel electrophoresis prior to in-gel trypsin digestion. Peptides were identified by tande...
Research Interests:
Research Interests:
Research Interests:
Research Interests: Chemistry, Kinetics, Mathematical Modeling, Experimental Design, Medicine, and 15 moreMethods, Diffusion, Photobleaching, Green Fluorescent Protein, Clinical Sciences, Mathematical Model, Diffusion Coefficient, Protein Domains, Fluorescent Protein, Nucleus, Dissociation Constant, Molecular Interactions, Nuclear Dynamics, fibroblasts, and Live Cell Analysis
Research Interests: Mass Spectrometry, Biology, DNA damage, Medicine, Signal Transduction, and 12 moreBiological Sciences, Humans, Animals, Phosphorylation, Mitogen Activated Protein Kinase, CHEMICAL SCIENCES, Reproducibility of Results, Amino Acid Sequence, Recombinant Proteins, Proteome, Phosphopeptides, and Molecular Sequence Data
Research Interests:
Poly(ADP-ribose) polymerase 3 (PARP-3) is a novel member of the PARP family of enzymes that synthesize poly(ADP-ribose) on themselves and other acceptor proteins. Very little is known about this PARP, which is closely related to PARP-1... more
Poly(ADP-ribose) polymerase 3 (PARP-3) is a novel member of the PARP family of enzymes that synthesize poly(ADP-ribose) on themselves and other acceptor proteins. Very little is known about this PARP, which is closely related to PARP-1 and PARP-2. By sequence analysis, we find that PARP-3 may be expressed in two isoforms which we studied in more detail to gain insight into their possible functions. We find that both PARP-3 isoforms, transiently expressed as GFP or FLAG fusions, are nuclear. Detection of endogenous PARP-3 with a specific antibody also shows a widespread nuclear distribution, appearing in numerous small foci and a small number of larger foci. Through co-localization experiments and immunoprecipitations, the larger nuclear foci were identified as Polycomb group bodies (PcG bodies) and we found that PARP-3 is part of Polycomb group protein complexes. Furthermore, using a proteomics approach, we determined that both PARP-3 isoforms are part of complexes comprising DNA-PKcs, PARP-1, DNA ligase III, DNA ligase IV, Ku70, and Ku80. Our findings suggest that PARP-3 is a nuclear protein involved in transcriptional silencing and in the cellular response to DNA damage.
Research Interests: Mass Spectrometry, Biology, DNA damage, DNA repair, Medicine, and 15 moreDNA, Cercopithecus aethiops, Cell line, Humans, Animals, Immunoprecipitation, Chromatin, Isoenzymes, Amino Acid Sequence, Base Sequence, Cell Cycle Proteins, DNA binding proteins, Molecular and Cellular Biochemistry, Biochemistry and cell biology, and Molecular Sequence Data
Research Interests:
PARG [poly(ADP-ribose) glycohydrolase] is the only known enzyme that catalyses the hydrolysis of poly(ADP-ribose), a branched polymer that is synthesized by the poly(ADP-ribose) polymerase family of enzymes. Poly(ADP-ribosyl)ation is a... more
PARG [poly(ADP-ribose) glycohydrolase] is the only known enzyme that catalyses the hydrolysis of poly(ADP-ribose), a branched polymer that is synthesized by the poly(ADP-ribose) polymerase family of enzymes. Poly(ADP-ribosyl)ation is a transient post-translational modification that alters the functions of the acceptor proteins. It has mostly been studied in the context of DNA-damage signalling or DNA transaction events, such as replication and transcription reactions. Growing evidence now suggests that poly(ADP-ribosyl)ation could have a much broader impact on cellular functions. To elucidate the roles that could be played by PARG, we performed a proteomic identification of PARG-interacting proteins by mass spectrometric analysis of PARG pulled-down proteins. In the present paper, we report that PARG is resident in FMRP (Fragile-X mental retardation protein)-associated messenger ribonucleoparticles complexes. The localization of PARG in these complexes, which are components of the t...
Research Interests:
Research Interests: Kinetics, Medical Microbiology, DNA damage, Western blotting, Biological Sciences, and 15 moreDNA, Humans, Diffusion, Physical sciences, Enzyme, Subcellular Localization, Neuroblastoma, Cell nucleus, Isoenzymes, DNA damage response, Subcellular Fractions, Fusion Protein, Cytoplasm, Frap, and Biochemistry and cell biology
The BRCA1-associated deubiquitylase BAP1 is mutated in several cancers, most notably mesothelioma and melanoma, where it is thought to promote oncogenesis. In this study, we present evidence that BAP1 functions as part of the DNA damage... more
The BRCA1-associated deubiquitylase BAP1 is mutated in several cancers, most notably mesothelioma and melanoma, where it is thought to promote oncogenesis. In this study, we present evidence that BAP1 functions as part of the DNA damage response (DDR). We found that BAP1 mediates rapid poly(ADP-ribose)-dependent recruitment of the polycomb deubiquitylase complex PR-DUB to sites of DNA damage. Furthermore, we identified BAP1 as a phosphorylation target for the DDR kinase ATM. Functionally, BAP1 promoted repair of DNA double-strand breaks, enhancing cell survival after DNA damage. Our results highlight the importance of ubiquitin turnover at sites of DNA damage, and they provide a mechanism to account for the tumor-suppressive function of BAP1.
Research Interests: Cancer, Biology, DNA repair, Medicine, Humans, and 4 moreOsteosarcoma, Transfection, Germline, and lung neoplasms
The review begins with a concise description of the principles of phase separation. This is followed by a comprehensive section on phase separation of chromatin, in which we recount the 60 years history of chromatin aggregation studies,... more
The review begins with a concise description of the principles of phase separation. This is followed by a comprehensive section on phase separation of chromatin, in which we recount the 60 years history of chromatin aggregation studies, discuss the evidence that chromatin aggregation intrinsically is a physiologically relevant liquid–solid phase separation (LSPS) process driven by chromatin self-interaction, and highlight the recent findings that under specific solution conditions chromatin can undergo liquid–liquid phase separation (LLPS) rather than LSPS. In the next section of the review, we discuss how certain chromatin-associated proteins undergo LLPS in vitro and in vivo. Some chromatin-binding proteins undergo LLPS in purified form in near-physiological ionic strength buffers while others will do so only in the presence of DNA, nucleosomes, or chromatin. The final section of the review evaluates the solid and liquid states of chromatin in the nucleus. While chromatin behaves ...
Research Interests:
SUMMARYThe association of nuclear DNA with histones to form chromatin is essential to the temporal and spatial control of eukaryotic genomes. In this study, we examined the physical state of chromatin in vitro and in vivo. Our in vitro... more
SUMMARYThe association of nuclear DNA with histones to form chromatin is essential to the temporal and spatial control of eukaryotic genomes. In this study, we examined the physical state of chromatin in vitro and in vivo. Our in vitro studies demonstrate that MgCl2-dependent self-association of native chromatin fragments or reconstituted nucleosomal arrays produced supramolecular condensates whose constituents are physically constrained and solid-like. Liquid chromatin condensates could be generated in vitro, but only using non-physiological conditions. By measuring DNA mobility within heterochromatin and euchromatin in living cells, we show that chromatin also exhibits solid-like behavior in vivo. Representative heterochromatin proteins, however, displayed liquid-like behavior and coalesced around a solid chromatin scaffold. Remarkably, both euchromatin and heterochromatin showed solid-like behavior even when transmission electron microscopy revealed limited interactions between c...
An emerging principle of cellular compartmentalization is that liquid unmixing results in formation of compartments by phase separation. We used electron spectroscopic Imaging (ESI), a transmission electron microscopy technology, to... more
An emerging principle of cellular compartmentalization is that liquid unmixing results in formation of compartments by phase separation. We used electron spectroscopic Imaging (ESI), a transmission electron microscopy technology, to distinguish chromatin and nucleoplasmic phases of mammalian cell lines and their responses towards different environmental changes. We tested the hypothesis that charge-dependent phase separation mediated by the histone N-termini could explain the organization of chromatin. 3D images of nuclear chromatin with electron spectroscopic imaging (ESI) demonstrates that the amount of chromatin proximal to the interchromatin compartment (IC) differs between cell types, reflecting major differences in chromatin organization. These differences were lost when cells were treated overnight with a histone deacetylase inhibitor. We show that drastic, reversible changes in chromatin mixing or unmixing with the nucleoplasm/interchromatin space can be induced by modulatin...
Histones H1 or linker histones are highly dynamic proteins that diffuse throughout the cell nucleus and associate with chromatin (DNA and associated proteins). This binding interaction of histone H1 with the chromatin is thought to... more
Histones H1 or linker histones are highly dynamic proteins that diffuse throughout the cell nucleus and associate with chromatin (DNA and associated proteins). This binding interaction of histone H1 with the chromatin is thought to regulate chromatin organization and DNA accessibility to transcription factors and has been proven to involve a kinetic process characterized by a population that associates weakly with chromatin and rapidly dissociates and another population that resides at a binding site for up to several minutes before dissociating. When considering differences between these two classes of interactions in a mathematical model for the purpose of describing and quantifying the dynamics of histone H1, it becomes apparent that there could be several assembly pathways that explain the kinetic data obtained in living cells. In this work, we model these different pathways using systems of reaction-diffusion equations and carry out a model comparison analysis using FRAP (fluor...