Histone genes of the sea urchin (S. purpuratus) cloned in E coli: order, polarity, and strandedness of the five histone-coding and spacer regions.

Sea urchin (S. purpuratus) histone DNA of constructed plasmid chimeras cloned in E. coli was cleaved with the restriction endonucleases Eco RI, Hind III, Sal I. Bam I, and Hha I. The resulting fragments were ordered and isolated directly from agarose gels or cloned into other plasmids. Each fragment hybridized to one or another of the five histone mRNAs and elucidated the order of the histone genes in each of the cloned fragments. Some DNA did not hybridize to histone mRNAs and was identified as spacer DNA located between coding regions. Total sea urchin DNA was cleaved with restriction endonucleases, fractionated on agarose gels, and hybridized to histone mRNAs or histone DNA. The results revealed the order of the five histone genes in the histone gene repeat unit and demonstrate that the histone spacer DNA have little sequence homology to other genes. ExonucleaseIII digestion of specific linear chimeric histone DNA plasmids followed by hybridization with mRNAs demonstrated the existence of all five histone genes on one strand of DNA and the 5'-3' polarity of that strand. These results, in conjunction with the data of Wu et al. (1976), allow us to construct a map of coding and spacer sequences in the transcribed strand of S. purpuratus histone gene repeat unit: (see article).