Structure and expression in L-cells of a cloned H4 histone gene of the mouse

Abstract

We have cloned a chromosomal DNA fragment, mus-hi-1, from mouse C3H embryos and have shown that it contains an H4 histone gene together with spacer DNA but no other histone genes. Extensive portions of this 5.2 × 10 3 base long fragment have been sequenced, including the structural H4 gene and its surroundings. Impressive homologies to the previously studied histone genes have been found. The mouse H4 gene as with other histone genes, does not contain introns. Regulatory sequence elements found at the borders of lower eukaryotic histone genes are also present near the mouse H4 gene. However, unlike sea urchin or Drosophila, mouse does not seem to have a major histone DNA repeat unit. Altogether about 30 H4 histone genes were found to be distributed over at least 11 genomic restriction fragments of different sizes. The H4 gene described here belongs to a minor class of histone genes which is nevertheless expressed in mouse L-cells as judged by S 1 nuclease protection experiments. The cloned H4 gene was used to determine the size of histone primary transcripts. High molecular weight precursors of H4 mRNA could not be detected by any of the methods used, hence the most probable mode of transcription of the H4 gene in L-cells is monocistronic.