DNA sequences homologous to long double-stranded RNA. Transcription of intracisternal A-particle genes and major long repeat of the mouse genome

Abstract

Long double-stranded RNA (dsRNA-A) (Kramerov, D.A., Ryskov, A.P. and Georgiev, G.P. (1977) Biochim. Biophys. Acta 475, 461-475) from Ehrlich ascites carcinoma cells was used for the search for mobile dispersed genes in the mouse genome. Two kinds of genomic sequences hybridizing to dsRNA-A were cloned. They were designated A1 and A2. The A1 sequence was identified as the gene for intracisternal A particles, while the A2 sequence was found to be the major long repetitive sequence of the mouse genome. Melted dsRNA-A hybridized equally well to both DNA strands of A1 and A2 sequences while total poly(A)+ RNA bound preferentially to one of them. Thus, a partially symmetrical transcription took place in the case of A1 and A2 elements. The analysis of transcripts of A1 elements in Ehrlich carcinoma cells revealed RNAs with sizes of 9.5 kb, 6.8 kb and 6.0 kb. In plasmocytoma MOPC 21 cells, instead of the 6.0 kb RNA, two other kinds of RNA with sizes 5.3 kb and 7.8 kb were found. These transcripts poorly coincided with the four known variants of intracisternal A-particle (IAP) genes. It seemed that at least some of the described RNAs were transcribed from some minor non-identified variants of IAP genes. The A2 transcripts were practically restricted to nuclei, their sizes being heterogeneous.