mRNA levels of the linker histone variant, H1o, in mitotically active human diploid fibroblasts as a function of the phases of the cell cycle and cumulative population doublings.

摘要

Senescence and differentiation have many similarities with respect to certain aspects of gene expression and cell cycle related events. One linker histone variant tightly associated with differentiation is the H1 variant, H1o. The work of this investigation has focused on the expression of H1o during the phases of the cell cycle and as a function of increasing cumulative population doublings (CPD) in an in vitro model ageing cell system, namely, human diploid fibroblasts. Increased H1o mRNA levels were found during the S phase of the cell cycle contrary to H1o protein relative synthesis rates, which were found to be increased during the Go phase of the cell cycle. These results were obtained in actively proliferating cell populations. However when the proliferative rate of the overall population begins to drop (CPD 50), H1o mRNA levels tend to remain stable throughout the Go, G1 and S phases. On the other hand, no changes in the H1o relative synthesis rates were found as a function of increasing CPD. Uncoupling of H1o protein and mRNA levels has been observed in numerous differentiating systems. The analogous mode in which H1o gene expression is regulated in both these two systems reinforces the opinion that senescence and differentiation may have similarities at the level of chromatin remodelling.