Potter S S, Branford W W
Division of Developmental Biology, Children's Hospital Medical Center and Department of Pediatrics, 3333 Burnet Ave., University of Cincinnati College of Medicine, Cincinnati, Ohio 45229-3039, USA.
Mamm Genome. 1998 Oct;9(10):799-806. doi: 10.1007/s003359900870.
We previously described the existence of abundant, processed, polyadenylated murine Hoxa 11 antisense transcripts. Of particular interest, in the developing limbs the antisense transcripts were observed to be present in a pattern complementary to that of the sense transcripts, suggesting a possible regulatory function (Hsieh-Li et al. 1995). We have analyzed the human HOXA 11 genomic locus, showing strong evolutionary conservation of regions potentially encoding antisense transcripts. Human HOXA 11 fetal kidney antisense cDNAs were identified and sequenced, demonstrating the evolutionary conservation of Hoxa 11 antisense transcription. As for the mouse, the human antisense RNAs were polyadenylated and showed several alternative processing patterns, but shared the sequences of a common 3' exon. The evolutionary conservation of the opposite strand transcripts strongly suggests function. A significantly long open reading frame was observed, but mouse-human comparisons argued against true coding function. Murine kidney Hoxa 11 antisense transcription and processing was also examined, revealing tissue-specific differences between limb and kidney. A novel procedure, designated Race in Circles, was devised and used to define mouse limb antisense transcription start sites. Furthermore, comparisons of human, mouse, and chicken sense transcript Hoxa 11 homeobox nucleotide sequences and their respective encoded homeodomains indicate a very strong selective pressure in vertebrates against mutations that result in coding changes. Given the significant differences in amino acid sequences of the homeodomains of different Hox genes, this observation argues for individual homeodomain functional specificity.
我们之前描述过大量经过加工的、多聚腺苷酸化的小鼠Hoxa 11反义转录本的存在。特别值得注意的是，在发育中的肢体中，观察到反义转录本以与有义转录本互补的模式存在，这表明其可能具有调控功能（谢立等人，1995年）。我们分析了人类HOXA 11基因组位点，发现潜在编码反义转录本的区域具有很强的进化保守性。鉴定并测序了人类HOXA 11胎儿肾脏反义cDNA，证明了Hoxa 11反义转录的进化保守性。与小鼠一样，人类反义RNA也进行了多聚腺苷酸化，并呈现出几种不同的加工模式，但共享一个共同3'外显子的序列。相反链转录本的进化保守性强烈表明其具有功能。观察到一个显著长的开放阅读框，但小鼠与人类的比较结果表明其不具有真正的编码功能。还研究了小鼠肾脏Hoxa 11反义转录和加工情况，揭示了肢体和肾脏之间的组织特异性差异。设计并使用了一种名为“循环Race”的新方法来确定小鼠肢体反义转录起始位点。此外，对人类、小鼠和鸡的有义转录本Hoxa 11同源框核苷酸序列及其各自编码的同源结构域进行比较，表明脊椎动物对导致编码变化的突变具有很强的选择压力。鉴于不同Hox基因同源结构域的氨基酸序列存在显著差异，这一观察结果支持了单个同源结构域的功能特异性。
