Isolation of the gene for the testis-specific H1 histone variant H1t

H1t is a testis-specific H1 variant found in pachytene spermatocytes and round spermatids of mammals. The H1t gene was isolated from the Sargent-Bonner library of recombinant lambda bacteriophage containing EcoRI fragments of rat liver DNA using a hybridization probe derived from a chicken H1 variant. The rat H1t gene encodes a 207-amino acid protein (ignoring the initiating methionine) that matches perfectly what is known of the sequence and composition of H1t isolated from rat testes. The gene lacks introns and has good matches to all the consensus sequences known to lie upstream from a variety of H1 genes from diverse organisms. It also has the standard downstream palindromic sequence that specifies the 3'-end of most histone messages. Accordingly, the features of the gene or its environs that restrict its expression to a particular phase of spermatogenesis are not yet evident.