Pollock P M, Stark M S, Palmer J M, Walters M K, Aitken J F, Martin N G, Hayward N K
Joint Experimental Oncology Program of the Queensland Institute of Medical Research, University of Queensland, and the Queensland Cancer Fund, P.O. Royal Brisbane Hospital, Brisbane, Australia.
Genes Chromosomes Cancer. 2001 Sep;32(1):89-94. doi: 10.1002/gcc.1170.
Approximately 50% of all melanoma families worldwide show linkage to 9p21-22, but only about half of these have been shown to contain germ line CDKN2A mutations. It has been hypothesized that a proportion of these families carry mutations in the noncoding regions of CDKN2A. Several Canadian families have been reported to carry a mutation in the 5' UTR, at position -34 relative to the start site, which gives rise to a novel AUG translation initiation codon that markedly decreases translation from the wild-type AUG (Liu et al., 1999). Haplotype sharing in these Canadian families suggested that this mutation is of British origin. We sequenced 1,327 base pairs (bp) of CDKN2A, making up 1,116 bp of the 5' UTR and promoter, all of exon 1, and 61 bp of intron 1, in at least one melanoma case from 110 Australian families with three or more affected members known not to carry mutations within the p16 coding region. In addition, 431 bp upstream of the start codon was sequenced in an additional 253 affected probands from two-case melanoma families for which the CDKN2A mutation status was unknown. Several known polymorphisms at positions -33, -191, -493, and -735 were detected, in addition to four novel variants at positions 120, -252, -347, and -981 relative to the start codon. One of the probands from a two-case family was found to have the previously reported Q50R mutation. No family member was found to carry the mutation at position -34 or any other disease-associated mutation. For further investigation of noncoding CDKN2A mutations that may affect transcription, allele-specific expression analysis was carried out in 31 of the families with at least three affected members who showed either complete or "indeterminate" 9p haplotype sharing without CDKN2A exonic mutations. Reverse transcription polymerase chain reaction and automated sequencing showed expression of both CDKN2A alleles in all family members tested. The lack of CDKN2A promoter mutations and the absence of transcriptional silencing in the germ line of this cohort of families suggest that mutations in the promoter and 5' UTR play a very limited role in melanoma predisposition.
全球所有黑素瘤家族中约50%显示与9p21 - 22连锁，但其中只有约一半被证明含有种系CDKN2A突变。据推测，这些家族中有一部分携带CDKN2A非编码区的突变。据报道，几个加拿大家族在5' UTR的相对于起始位点-34的位置携带一个突变，该突变产生一个新的AUG翻译起始密码子，显著降低了从野生型AUG的翻译水平（Liu等人，1999年）。这些加拿大家族中的单倍型共享表明该突变起源于英国。我们对110个有三个或更多受影响成员且已知在p16编码区内不携带突变的澳大利亚家族中至少一例黑素瘤病例的CDKN2A的1327个碱基对（bp）进行了测序，其中包括5' UTR和启动子的1116 bp、整个外显子1以及内含子1的61 bp。此外，对另外253例来自两例黑素瘤家族且CDKN2A突变状态未知的先证者，在起始密码子上游431 bp处进行了测序。除了在相对于起始密码子的120、-252、-347和-981位置的四个新变体之外，还检测到了-33、-191、-493和-735位置的几个已知多态性。在一个两例家族的先证者中发现了先前报道的Q50R突变。未发现家族成员携带-34位置的突变或任何其他疾病相关突变。为了进一步研究可能影响转录的CDKN2A非编码突变，对31个有至少三个受影响成员且显示完全或“不确定”的9p单倍型共享且无CDKN2A外显子突变的家族进行了等位基因特异性表达分析。逆转录聚合酶链反应和自动测序显示在所有测试的家族成员中CDKN2A的两个等位基因均有表达。该家族队列种系中缺乏CDKN2A启动子突变且无转录沉默表明启动子和5' UTR中的突变在黑素瘤易感性中起的作用非常有限。
