Histones terminally differentiated cells

Phosphorylation of specialized linker histones (such as histone H5 or sperm-specific HI histones) has also been shown to have a major role in the chromatin folding processes leading to the highly condensed chromatin structure which is present in the nuclei of terminally differentiated cells such as bird erythrocytes [172] and histone-containing sperm nuclei [115,118]. In this later instance. 

Figure 3. Representative linker histone variants from human (Homo sapiens H.s.), and yeast (Saccha-romyces cerevisiae S.c.). The globular domain indicates the winged helix DNA binding domain that is common for all linker histones. Hlc is a typical somatic linker histone common for most cells. H° is expressed in all somatic cells, but is more abundant in terminally differentiated tissues. Hlfoo is an oocyte-specific linker histone. The structure of S. cerevisiae Hholp with two globular domains is a notable deviation...

Dey, B.K., Stalker, L., Schnerch, A., Bhatia, M., Taylor-Papidimitriou, J. and Wynder, C. (2008) The histone demethylase KDM5b/JARIDlb plays a role in cell fate decisions by blocking terminal differentiation. Molecular and Cellular Biology, 28, 5312-5327. 

The finding that nearly all of the conjugates except modified histone H2B and poly-(ADPR) synthase itself are also present in untreated normal hepatocytes (Figs. 5 and 6), supports the view that these proteins may be involved in other chromatin functions in addition to DNA repair. It is tempting to speculate that the higher degree of ADP-ribosylation of most of these proteins in the normal hepatocyte (Fig. 6 nh and It) as compared to the hepatoma cell (Fig. 6 hp) may be related to the terminally differentiated state of the normal liver cell. 

Jung, M., Brosch, G., Kolle, D., Scherf, H., Gerhauser, C. and Loidl, P. (1999) Amide analogues of trichostatin A as inhibitors of histone deacetylase and inducers of terminal cell differentiation. Journal of Medicinal Chemistry, 42, 4669-4679. 

Accordingly, some effort has been devoted to studying the effects of cisplatin on transcription. In vitro experiments with RNA polymerases demonstrated that productive elongation activity was prematurely terminated by the whole spectrum of cisplatin-DNA adducts, but not by the /ran.y-DDP 1,3-intrastrand adducts [150-152], Selective bypass of trans-DDP adducts was also demonstrated in XPA cells, suggesting that repair of the DNA lesions did not contribute to differential transcription inhibition by the platinum compounds [153], In vivo, hormone-induced chromatin remodeling and subsequent transcription from the MMTV promoter was specifically inhibited by cisplatin [154], In this case, platinum adducts seemed to cause a decrease in the DNA binding of one of the transcription factors, NF1. Several chromatin-associated proteins, such as the linker histone protein HI or... 

HMG protein-induce erythroleukemia cell differentiation. Friend virus-induced mouse erythroleukemia cells differentiate under the effects of hexamethylene bisacetamide (HMBA) and HMGl protein. Ca" " ionophore induced excess HMGl protein and promoted leukemia cell differentiation. Further inducers of leukemia cell differentiation are HDAC inhibitors h)q)eracetylating N-terminal tails of core histones H3/4 (trichostatin), DMSO, phorbol myristate acetate (PMA), the activator of PKC. ... 

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