BACKGROUND. The database of human Expressed Sequence Tags (dbEST) provides
a potential source for identification of tissue-specific genes. This databa
se contains sequences that originate from cDNA libraries from particular tu
mors, organs or cell typos. In this report, we have used the EST database t
o identify PRAC, a novel gene specifically expressed in human Prostate, pro
state 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 c
DNA libraries. The tissue specificity was examined by multiple tissue RNA d
ot blots and RT-PCR. The PRAC transcript and protein Mas identified using N
orthern 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. Thi
s transcript encodes a 6 kDa nuclear protein. The PRAC gene is located on c
hromosome 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, identifica
tion of potential phosphorylation sites, and possible cotranscription with
the Hoxb-13 gene suggest that PRAC may have a regulatory role in the nucleu
s. Prostate 47:125-131, 2001. (C) 2001 Wiley-Liss, Inc.