Terminally redundant sequences in cellular intracisternal A-particle genes.

The sequences coding for intracisternal A-particle RNA form a family of related but not identical genetic elements which are present in 650 to 1,000 copies within the mouse genome. We showed that different intracisternal A-particle genes had a terminally redundant sequence of about 400 base pairs, one-half of which arose from the 3' end of the intracisternal A-particle RNA. A second portion of the redundant region did not contain 3-related sequences and was probably derived from the 5' end of intracisternal A-particle RNA. Thus, there were endogenous intracisternal A-particle genes in the cellular DNA-3'-5'--3'-5'-cellular DNA configuration identified for type B and C retroviruses. This indicated that the initial integration of intracisternal A-particle genes into the Mus musculus genome occurred by the same mechanism as the integration of other retroviruses. Two types of heterogeneity were identified among the 5' sequences of the two genes.