Size and genetic composition of long terminal repeat sequences in the mouse intracisternal A-particle gene 81.

The intracisternal A-particle (IAP) genome is a retrovirus-like gene family. Over 1000 copies of IAP genes are dispersed throughout the mouse genome. The purpose of this study was to determine the nucleotide sequence of both ends of the long terminal repeat (LTR) units which bind the IAP gene 81. The results obtained showed that, whereas the structural domain and several genomic characteristics of the IAP 81 LTR units and other LTR structures of a given IAP gene were almost identical, the nucleotide sequences of these LTR units associated with different IAP gene were sometimes very different from each other. In the comparisons of different LTR structures, the transcriptional signals for promotion, initiation, polyadenylation and termination as well as several characteristic sequences of the Z-DNA region, enhancer core sequence and glucocorticoid-responsive element were all found to be present in IAP 81 LTRs. The possible roles of the primary nucleotide sequence of an LTR structure are discussed.