Wolf and co-workers proposed a reaction mechanism by which biotinidase catalyzes biotinylation of histones (Hymes et al., 1995). Subsequently, it was shown that biotinylation of histones occurs in vivo and that biotinylation of histones increases in response to cell proliferation (Stanley et al., 2001). Biotinylation of histones increases by approximately fourfold during G1, S, G2 and M
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Fig. 5.10. Levels of mRNA encoding holocarboxylase synthetase in cultured PBMCs. Cells were isolated from healthy adults and cultured in mitogen-containing medium (2.0 mg ml-1 pokeweed lectin) for 3 days; controls were cultured without pokeweed lectin. Total RNA was isolated and mRNA encoding holocarboxylase synthetase was quantitated by RT-PCR. P = pokeweed lectin; C = control (Stanley et al., 2002).
phase of the cell cycle compared with G0 phase. This finding is consistent with the hypothesis that increased biotinylation of histones in proliferating PBMCs generates an increased demand for biotin. Biotinylation of histones in quiescent and proliferating PBMCs is discussed extensively in Chapter 17.
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