No abstract

The proliferation of the human promonocytic leukemia cell line U937 is inhibited by several ether lipids, ether lipid analogues and by phorbol esters. An early effect of this retardation of cell growth is the induction of a basic chromosomal protein, histone H1(0). Northern blot analysis of H1(0) mRNA levels reveals an increase of the mRNA concentration within a few hours after addition of hexadecylphosphocholine and 1-O-octadecyl-2-O-methyl-rac-glycero-3-phosphocholine. This early effect on the synthesis of a subtype of H1 proteins precedes the expression of several parameters of the monocytic differentiation of U937 cells.

The expression of a human histone H1 isoform (H1.1) was studied in several human tissues. Northern blot analysis has revealed that this gene is expressed in testis and thymus, but not in other human tissues. In this report, we demonstrate that the expression of the histone H1.1 gene in human testis is restricted to early round spermatids that belong to the fraction of postmeiotic sperm cells. Transcripts hybridizing with the human H1.1 gene could not be detected in testis of mouse, rat, bull or boar. Southern blot analysis with human genomic DNA, DNA from different Old World monkeys (chimpanzee, orangutan, gorilla and rhesus monkey) and DNA from several mammalian species has revealed that the histone H1.1 gene is highly conserved in higher primates, whereas no cross-hybridization can be detected with DNA from other mammalian species such as mouse, rat, hamster or bull. In a previous report, the human histone H1.1 gene and other H1 genes (H1.2-H1.5, H1t) were assigned to chromosome 6 by polymerase chain reaction analysis using human-rodent cell hybrid DNA; fluorescence in situ hybridization indicated that these genes form part of a major gene cluster on the short arm of chromosome 6. We have confirmed the localization of histone H1.1 to chromosome 6 and have regionally assigned the locus to 6p21.3 by radioactive in situ hybridization.

No abstract

The expression of the human H1 zero histone gene and of a main type H1 gene was analyzed in two human leukemia cell lines. The main type, replication dependent H1 gene expression reflected the state of proliferation of both cell lines. No H1 zero mRNA was detected in the promyelocytic HL-60 line, whereas the monocytic U937 cells showed low steady-state levels of 1H zero mRNA. Stimulation of HL-60 with several known inducers of differentiation failed to induce any accumulation of H1 zero mRNA. Treatment of U937 with phorbol ester or butyrate, on the other hand, led to an increase of the H1 zero mRNA concentration.