Isolation and characterization of a novel cDNA, UBAP1, derived from the tumor suppressor locus in human chromosome 9p21-22

Purpose: To clone the putative tumor suppressor gene(s) in a refined region at 9p21-22 undergoing loss of heterozygosity in nasopharyngeal carcinoma ( NPC). Methods: We systematically screened the expression patterns of 25 nov el ESTs (expressed sequence tags) in a minimal common deleted region of 9p2 1-22 in NPC. One of these ESTs was found down-regulated in NPC. Subsequentl y, the corresponding gene sequence of this EST was established by cDNA clon ing and RACE (rapid amplification of cDNA end) procedures. Furthermore, a m ouse homologue of this gene was identified. The expression of this gene was examined using Northern blot or reverse transcription-polymerase chain rea ction (RT-PCR) in various human and mouse tissues. A limited screen for mut ation of coding sequence of this novel human gene was undertaken using RT-P CR and direct sequencing analysis. Results: A novel gene was cloned. This g ene is a new member of the UBA domain family, so we named it UBAP1 for ubiq uitin-associated protein I (HUGO Gene Nomenclature Committee-approved symbo l). Northern blot and RT-PCR analysis demonstrate a ubiquitous pattern of g ene expression in human and mouse tissues. The direct sequencing analysis o f the coding region of hU BAP1 following RT-PCR failed to reveal any mutati ons in a preliminary screen of NPC cell line HNE1 and primary nasopharyngea l carcinoma samples. Conclusions: We cloned a novel gene UBAP1, which is hi ghly conserved between human and mouse. Clearly, as a novel member of UBA d omain protein family and taking its map location into account, a more exten sive analysis is essential to establish whether subtle mutations are presen t in nasopharyngeal carcinomas.