INVERTED REPEATS ARE NECESSARY FOR CIRCULARIZATION OF THE MOUSE TESTIS SRY TRANSCRIPT

Circular non-polyadenylated RNA molecules have been identified as stab le transcription products of the human ETS-1 and mouse Sry genes, RNA circularization has been proposed to require two steps, The first step utilizes intramolecular base pairing to produce a transient stem-loop structure. The second step involves splicing a downstream donor splic e site (DSS) to a now closely appositioned upstream acceptor splice si te (ASS) within the loop. We demonstrate that the presence of long inv erted repeats (IR) flanking the mouse Sry gene leads to the formation of the Sry circular transcript in cultured cells. Circularization requ ires the presence of both IR. As few as 400 complementary nt are neces sary for this process, The presence of the IR does not significantly s timulate intermolecular annealing and trans-splicing in vivo.