Non-histone chromosomal proteins: their role in the regulation of histone-gene expression.
Histone-gene expression was studied during the cell cycle of continuously dividing HeLa S3 cells and after stimulation of confluent monolayers of WI-38 human diploid fibroblasts to proliferate. The presence of histone-mRNA sequences was assayed by hybridization to a 3H-labelled single-stranded DNA complementary to histone-mRNA molecules. In HeLa S3 cells histone mRNA sequences were found in the nucleus and associated with polyribosomes during S-phase, but not during G1-phase. Transcripts of S-phase chromatin contained histone-mRNA sequences, but those of G1-phase chromatin did not. Similarly, in WI-38 cells association of histone-mRNA sequences with polyribosomes and transcription of histone-mRNA sequences from chromatin parallel DNA replication. Taken together these results suggest that the regulation of histone-gene expression resides, at least in part, at the transcriptional level. Chromatin-reconstitution studies provide evidence that non-histone chromosomal proteins play a key role in activation of histone-gene transcription during the period of the cell cycle when DNA is replicated. Phosphate groups associated with the S-phase non-histone chromosomal proteins appear to be functionally involved in the control of histone-gene readout.
D000818:Animals; D002453:Cell Cycle; D002843:Chromatin / Q000378:metabolism; D002868:Chromosomal Proteins, Non-Histone / Q000235:genetics*; D004247:DNA / Q000096:biosynthesis; D005347:Fibroblasts / Q000378:metabolism; D006657:Histones / Q000235:genetics*; D006801:Humans; D007700:Kinetics; D008938:Mitosis; D008954:Models, Biological; D009693:Nucleic Acid Hybridization; D010750:Phosphoproteins / Q000096:biosynthesis; D011132:Polyribosomes / Q000378:metabolism; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000378:metabolism; D012335:RNA, Ribosomal / Q000378:metabolism; D014158:Transcription, Genetic
D002843:Chromatin; D002868:Chromosomal Proteins, Non-Histone; D006657:Histones; D010750:Phosphoproteins; D012333:RNA, Messenger; D012335:RNA, Ribosomal; D004247:DNA