PRAC: A novel small nuclear protein that is specifically expressed in human prostate and colon

Abstract

BACKGROUND The database of human Expressed Sequence Tags (dbEST) provides a potential source for identification of tissue‐specific genes. This database contains sequences that originate from cDNA libraries from particular tumors, organs or cell types. In this report, we have used the EST database to identify PRAC, a novel gene specifically expressed in human Prostate, prostate cancer, Rectum And distal Colon. METHODS Using a computer based analysis, a cluster of sequence homologous ESTs was identified which contained ESTs derived only from human prostate cDNA libraries. The tissue specificity was examined by multiple tissue RNA dot blots and RT‐PCR. The PRAC transcript and protein was identified using Northern blot analysis, RACE‐PCR, primer extension, and western blot. RESULTS PRAC encode a 382 nucleotide RNA found in prostate, rectum, distal colon, and in three prostate cancer cell lines; LNCaP, PC‐3 and DU145. This transcript encodes a 6 kDa nuclear protein. The PRAC gene is located on chromosome 17 at position 17q21, about 4 kbp downstream from the homeodomain Hoxb‐13 gene. CONCLUSIONS Our data proves that the EST database can be a useful tool for discovery of prostate‐specific genes. The nuclear localization, identification of potential phosphorylation sites, and possible cotranscription with the Hoxb‐13 gene suggest that PRAC may have a regulatory role in the nucleus. Prostate 47:125–131, 2001.