Sequence organization of cloned intracisternal A particle genes.

Seven recombinant DNA clones containing mouse intracisternal A particle genes were isolated and analyzed by restriction enzyme digestion, Southern blot analysis and heteroduplex mapping. The sequence organization of the individual genes was found to differ, with one end of the gene region being most variable, while a central segment of 1.8 kb was missing from two of the clones. A third region, common to all the clones and containing the 3' end of the gene, is present in about 1800 copies per haploid genome, but the central portion is found in only 650 copies. The same reiteration frequency is found in both myeloma tumor and mouse liver DNA. The most abundant intracisternal A particle RNA in two different myeloma lines was found to be 3.5 kb, and RNA/DNA hybrids show that the RNA is homologous to all but a small internal segment of one of the clones.