CIRCULAR TRANSCRIPTS OF THE TESTIS-DETERMINING GENE SRY IN ADULT-MOUSE TESTIS

Sry is expressed at higher levels in the adult testis, where no functi on has been determined, than in the genital ridge, its critical site o f action. cDNA and 5' RACE clones isolated from testis or from Sry-tra nsfected cell lines have an unusual structure, with 3' sequences locat ed in a 5' position. RNAase protection assays and reverse transcriptio n polymerase chain reactions confirmed that these unusual RNA molecule s represent the most abundant transcript in testis. Furthermore, oligo nucleotide hybridization and RNAase H digestion proved that these Sry RNA molecules are circular. Similar transcripts were detected in the t estes of mice with Mus musculus musculus, Mus musculus domesticus, and Mus spretus Sry genes. The circular RNA is found in the cytoplasm but is not substantially bound to polysomes. We suggest that the circles arise from normal splicing processes as a consequence of the unusual g enomic structure surrounding the Sry locus in the mouse.