Sequence and expression of chicken beta A2- and beta B3-crystallins
Sequence and expression of chicken beta A2- and beta B3-crystallins
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DOI：
10.1006/exer.1996.0013
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发表时间：
1996-01-01
影响因子：
3.4
通讯作者：
Piatigorsky, J
中科院分区：
文献类型：
--
作者：
Duncan, MK;BanerjeeBasu, S;Piatigorsky, J
晶状体蛋白是一组不同的蛋白质，其有助于眼睛透镜的透明度和折射特性。在此之前，已经克隆和测序了六种已知牛β-晶体蛋白基因中的四种的鸡直系同源物。在本研究中，已分离出与鸡β A2-和β B3-晶状体蛋白（两种先前未鉴定的鸡β-晶状体蛋白）的直系同源物相对应的cDNA。此外，三个独立的鸡β B2-晶体蛋白cDNA的序列分析产生了推导的连接肽序列，这是相当短的比以前报道的。因此，所有已知牛β-晶状体蛋白的直接同源物在鸡透镜中表达。这表明，导致已知脊椎动物β-晶体蛋白的复制发生在3亿多年前。β B2-和β B3/A1-晶状体蛋白是最高度保守的β-晶状体蛋白，这表明这些基因除了在透镜中的屈光作用外，可能对其他功能也很重要。通过北方印迹杂交分析，β A2-和β B3-晶状体蛋白在鸡胚中均显示晶状体特异性。β A_2-晶状体蛋白的相对含量从胚胎发育的第5天到成年一直保持稳定，而β B_3-晶状体蛋白的相对含量则一直增加到出壳，并且在成年透镜中的含量略低。在5天鸡胚的透镜上皮细胞和纤维中，β A_2-晶状体蛋白mRNA的相对含量大致相等;相反，β B3-晶状体蛋白mRNA在透镜纤维中优先检测到。这些数据结合以前的研究表明，β-晶体蛋白基因的调节独立于彼此在发育中的鸡透镜。所有7个鸡β-晶体蛋白多肽的一级结构的阐明将有利于未来的研究结构/功能关系负责透镜透明度和β-晶体蛋白基因表达的分子基础上，在发展过程中。(C)1996年学术出版社
Crystallins are a diverse group of proteins that contribute to the transparency and refractive properties of the eye lens. Previously, the chicken orthologs of four out of the six known bovine beta-crystallin genes have been cloned and sequenced. In the present study, cDNAs corresponding to the chicken orthologs of beta A2- and beta B3-crystallin, the two previously unidentified chicken beta-crystallins, have been isolated. In addition, sequence analysis of three independent chicken beta B2-crystallin cDNAs yielded a deduced connecting peptide sequence which is considerably shorter than that reported previously. Thus, direct homologs of all of the known bovine beta-crystallins are expressed in the chicken lens. This demonstrates that the duplications giving rise to the known vertebrate beta-crystallins occurred over 300 million years ago. beta B2- and beta B3/A1-crystallin are the most highly conserved of the beta-crystallins suggesting that these genes may be important for other functions besides their refractive role in the lens. By Northern blot hybridization analysis, both beta A2- and beta B3-crystallin were shown to be lens-specific in the chicken embryo. The relative levels of beta A2-crystallin remained stable from five days of embryogenesis until adulthood, while the relative amounts of beta B3-crystallin increased until hatching and were appreciably lower in the adult lens, Approximately equal relative amounts of beta A2-crystallin mRNA were found in the lens epithelia and fibers of 5 day embryonic chicken embryos; by contrast, beta B3-crystallin mRNA was detected preferentially in the lens fibers. These data in combination with previous studies suggest that beta-crystallin genes are regulated independently from each other in the developing chicken lens. The elucidation of the primary structures for all seven chicken beta-crystallin polypeptides will facilitate future studies on the structure/function relationships responsible for lens transparency and on the molecular basis for beta-crystallin gene expression during development. (C) 1996 Academic Press Limited