Lin B, Rommens J M, Graham R K, Kalchman M, MacDonald H, Nasir J, Delaney A, Goldberg Y P, Hayden M R
Department of Medical Genetics, University of British Columbia, Vancouver, Canada.
Hum Mol Genet. 1993 Oct;2(10):1541-5. doi: 10.1093/hmg/2.10.1541.
Recently a novel gene containing a CAG trinucleotide repeat that is expanded on HD chromosomes has been identified(1). This gene was shown to detect a single transcript of 10-11 kb by RNA hybridization. We have however, previously identified three cDNAs which are part of the same gene that have been shown to detect two distinct transcripts of 10 kb and one that is significantly larger(2,3). These different mRNA species could be due to use of alternate transcription start sites, alternate splicing or selection of different polyadenylation sites. We have identified cDNA clones spanning the HD gene including two (HD12 and HD14) that share identical protein coding sequences but differ in size and sequence of their 3' untranslated region. HD14 has 3,360 base pairs of additional sequence distal to the previously published 3' end (1). RNA hybridization has revealed that the larger 13.7 kb fragment is the predominant transcript in human brain. cDNA fragments unique to HD14 detected only the larger transcript. Sequence analysis identified two different putative polyadenylation sequences at position 10,326 and 13,645 of the HD14 cDNA. These findings indicate that the two observed mRNA species originate from a single gene and that differential polyadenylation leads to transcripts of different size. The relative increased abundance of the larger transcript in human brain may provide some insights into the mechanism by which a widely expressed gene may exert tissue specific effects.
最近，一个含有CAG三核苷酸重复序列且在亨廷顿舞蹈症（HD）染色体上发生扩增的新基因已被鉴定出来(1)。通过RNA杂交显示，该基因可检测到一个10 - 11 kb的单一转录本。然而，我们之前已鉴定出三个属于同一基因的cDNA，它们已被证明可检测到10 kb的两种不同转录本以及一种明显更大的转录本(2,3)。这些不同的mRNA种类可能是由于使用了不同的转录起始位点、选择性剪接或不同聚腺苷酸化位点的选择。我们已鉴定出跨越HD基因的cDNA克隆，其中两个（HD12和HD14）具有相同的蛋白质编码序列，但3'非翻译区的大小和序列不同。HD14在先前公布的3'末端远端还有3360个碱基对的额外序列(1)。RNA杂交显示，较大的13.7 kb片段是人类大脑中的主要转录本。HD14特有的cDNA片段仅检测到较大的转录本。序列分析在HD14 cDNA的第10326位和13645位鉴定出两个不同的假定聚腺苷酸化序列。这些发现表明，观察到的两种mRNA种类源自单个基因，并且差异聚腺苷酸化导致不同大小的转录本。人类大脑中较大转录本相对丰度的增加可能为一个广泛表达的基因如何发挥组织特异性作用的机制提供一些见解。
