Two efficient ribosomal frameshifting events are required for synthesis of mouse mammary tumor virus gag-related polyproteins.

作者：Tyler Jacks, Kayla G. Townsley, HAROLD E. VARMUS, John E. Majors · 发表于：Proceedings of the National Academy of Sciences · 年份：1987 · DOI：10.1073/pnas.84.12.4298 · 被引用次数：208 · 研究领域：RNA and protein synthesis mechanisms、Herpesvirus Infections and Treatments、Virus-based gene therapy research

The primary translation products of retroviral pol genes are polyproteins initiated in an upstream gene (gag). To investigate the manner in which the gag-initiated polyproteins of the mouse mammary tumor virus are produced, we determined the nucleotide sequence of a 1.8-kilobase DNA fragment that spans the region between gag and pol in the C3H strain of mouse mammary tumor virus. The sequence reveals three overlapping open reading frames: the first encodes products of gag (p27gag and p14gag); the second encodes a protein domain of unknown function (termed X) that is highly related to a similarly positioned sequence in simian type D retroviruses and the viral protease (pro); and the third encodes the reverse transcriptase. The reading frames are organized to permit uninterrupted readthrough from gag to pol if ribosomal frameshifts occur in the -1 direction within each of the two overlapping regions, one of which is 16 nucleotides in length and the other 13 nucleotides. Cell-free translation of RNA containing these overlap regions shows that fusion of the reading frames by ribosomal frameshifting occurs efficiently: about one-fourth of the ribosomes traversing the gag-X/pro overlap and one-tenth traversing the X/pro-pol overlap shift frames, generating gag-related polyproteins in ratios similar to those observed in vivo. Synthetic oligonucleotides containing either of the overlap regions inserted into novel contexts do not induce frameshifting; hence the overlapping portions of...