ATYPICAL SPLICING OF THE LATENCY-ASSOCIATED TRANSCRIPTS OF HERPES-SIMPLEX TYPE-1

We previously have shown that two latency-associated transcripts (LATs ) of herpes simplex type 1 (HSV-1) are probably lariats, produced duri ng splicing. By RNaseH digestion analysis, we now show that the major branchpoint of the 2.0-kb LAT was within 46 nt 5' of the splice accept or site. A more detailed mapping by primer extension revealed the bran chpoint as an adenosine 29 nt 5' of the splice acceptor site. Introduc tion of two branchpoint sequences with good matches to the consensus a t position -25 had no effect on the splicing efficiency but reduced th e accumulation of the 2.0-kb LATs at least 90-fold. The second focus o f our studies was the 1.5-kb LAT. It was not detected by Northern anal yses in either productively infected or transfected cultured cells or even in cells of neuronal origin. However, it was detected in the trig eminal ganglia of mice experimentally infected with HSV-1 after 10 day s. Moreover, its abundance relative to that of the 2.0-kb species incr eased 4-fold from 10 to 30 days after infection, consistent with an in terpretation that the 1.5-kb species, once formed, was more stable tha n the 2.0-kb species. (C) 1998 Academic Press.