UBIQUITOUS EXPRESSION AND TESTIS-SPECIFIC ALTERNATIVE POLYADENYLATIONOF MESSENGER-RNA FOR THE HUMAN RAN GTPASE ACTIVATOR RANGAP1

RanGAP1 is the activator of the Ras-related nuclear GTPase Ran, which is involved in the nucleo-cytoplasmic transport of both, proteins and mRNAs, and also in cell cycle regulation. Here, we report a 2970-bp cD NA clone of RanGAP1 isolated from a HeLa lambda gt11 cDNA library. It contains a 215-bp 5' untranslated region (UTR) with a G+C-content of 6 8%, followed by a 1764-bp open reading frame and a 989-bp 3'UTR preced ing a 77-bp poly(A)(+) tail. RanGAP1 shows differential patterns of ex pression in human tissues. In addition to the 3.5-kb transcript presen t in all tissues and highly expressed in brain, thymus and testis, we found a second transcript of 2.8 kb in testis. In order to analyze thi s shorter transcript, we screened a human testis lambda gt10 cDNA libr ary and cloned an alternatively polyadenylated RanGAP1 transcript. Tak ing the 3' UTR of RanGAP1, which lies downstream of the first polyaden ylation signal, as a probe in Northern blot analysis, we confirmed tha t this second transcript found in testis results from a distinct 3' UT R.