A portion of all major classes of histone messenger RNA in amphibian oocytes is polyadenylated.

Abstract

Ovaries of the amphibian Triturus viridescens contain a considerable amount of 7 to 12 S RNA which fractionates with poly(A)+ RNA on oligo(dT)-cellulose column chromatography and directs the synthesis of all five classes of histones in a wheat germ cell-free system. The polyadenylate tracts associated with this 7 to 12 S poly (A)+ RNA are heterogeneous in length, ranging from approximately 60 to 120 nucleotides. Partially purified subfractions of histone mRNA templates were isolated from this RNA by preparative polyacrylamide gel electrophoresis. The correlation between the poly(A) content, the template activity in vitro, and the cell-free products encoded by these RNA subfractions suggests that Triturus ovary RNA contains poly(A)+ histone mRNA. The 7 to 12 S poly(A)+ RNA, but not 7 to 12 S poly(A)- RNA, is an effective template for the avian myeloblastosis virus reverse transcriptase-directed synthesis of complementary DNA (cDNA) in the presence of oligo(dT) primer. In the absence of primer, virtually no cDNA is synthesized. When cDNA complementary to 7 to 12 S poly(A)+ RNA is hybridized in situ to Drosophila melanogaster polytene chromosome preparations. cDNA hybrids are found primarily in the region 39D-E, the locus of the histone genes in Drosophila. This cDNA also hybridizes to the sea urchin histone gene sequences contained in the chimeric bacterial plasmids pSp2 and pSp17. These results provide strong evidence for the reality of polyadenylated histone mRNA in Triturus ovary.