Identification of human RNA transcripts among heterogeneous nuclear RNA from man-mouse somatic cell hybrids.

In man-mouse hybrid line from our cell library, the only cytological detectable portion of the human genome is the X chromosome, and the only genetic markers regularly expressed are coded by genes known to be ?X-linked. A component of the heterogeneous nuclear RNA of these cells was found to be complementary to repetitive human DNA sequences by means of RNA-DNA hybridization on nitrocellulose filters. The same procedure also permitted the identification of hybrid cell DNA sequences that are complementary to human heterogeneous nuclear RNA. This experimental approach, coupled with hybridization studies in situ, is expected to yield critical data on the distribution and the specificity of the repetitive DNA sequences present in the human genome and to provide a new tool for cytological mapping of human chromosomes.