家蚕多梳蛋白家族基因BmPsc的全长序列克隆及表达分析  

Full-length Cloning and Expression Analysis of Polycomb Group Protein Gene BmPsc in Silkworm,Bombyx mori

作　　者：徐曼[1] 谈娟[1] 张奎[1] 王雪[1] 崔红娟[1] 

机构地区：[1]家蚕基因组生物学国家重点实验室西南大学,重庆400715

出　　处：《蚕业科学》2013年第1期14-20,共7页ACTA SERICOLOGICA SINICA

基　　金：国家重点基础研究发展计划"973"项目(No.2012CB-114600);国家自然科学基金项目(No.31172268);西南大学研究生科技创新基金项目(No.ky2011002)

摘　　要：多梳蛋白(polycomb group,PcG)基因Bmi-1(B cell-specific MLV integration site-1)与人类造血干细胞以及多种肿瘤干细胞的维护相关,Bmi-1蛋白具有典型的N端Ring结构,通过结合核小体并抑制其重塑以实现抑制关键基因转录,具有沉默目的基因的功能。Bmi-1在昆虫中的同源基因为Psc(posterior sex combs)。采用RACE技术获得家蚕Psc基因(BmPsc)全长4 084 bp的序列。该基因位于家蚕第4号染色体上,是一个单外显子基因,ORF为3 291 bp,编码1 096个氨基酸,蛋白质分子质量121 kD,等电点(pI)为9.83;同源序列比对发现BmPsc与赤拟谷盗(Tribolium castaneum)的Psc基因序列有58%的相似度,与果蝇(Drosophila melanogaster)的Psc基因序列仅有34%的相似度;氨基酸序列分析显示BmPsc具有保守的N端Ring结构。利用qRT-PCR检测家蚕5龄第3天幼虫各组织以及5龄各时期幼虫血液中BmPsc基因的表达水平,发现BmPsc在各组织均有表达,在精巢以及卵巢中的表达明显较高,其次是翅原基(含造血器官),在循环血液中也有较高表达;在5龄各时期幼虫血液中的表达呈一定规律性,于蜕皮后的5龄第2天以及进入变态前的5龄第6天出现表达峰值,而在5龄中期(第4～5天)为表达低谷。研究结果为进一步阐释该基因在细胞水平以及个体水平对干细胞分化的抑制作用奠定了基础。Polycomb group protein （PcG） gene Bmi-1 （B cell-specific MLV integration site-1 ） is related to the maintenance of human hematopoietic stem cells and various cancerous stem cells. Protein Bmi-1 has a typical N-terminal Ring structure. It can bind to nucleosome and inhibit its remodeling to exert inhibition on key gene transcription, being capable of silencing target genes. The homologous gene of Bmi-1 in insects is Psc （posterior sex combs）. In present study, we obtained the full length （4 084 bp） of Psc gene in Bombyx mori （BmPsc） by means of RACE technology. BmPsc locates on the 4th Bombyx mori chromosome and has only one exon. It contains an open reading frame of 3 291 bp and encodes 1 096 amino acid residues with a calculated molecular mass of 121 kD and an isoelectric point of 9.83. Homologous sequence alignment showed that BmPsc shares 58% identity with Psc gene in Tribolium castaneum, while it has only 34% identity with that of Drosophila melanooaster.only 34% identity with that of Drosophila melanogaster. Analysis of amino acid sequence indicated that BmPsc possesses an N-terminal conserved Ring structure. The expression levels of BmPsc gene in various tissues of day 3 silkworm larvae of the 5th instar and hemolymph of the 5th instar larvae at different developmental stages were detected by qRT-PCR. It was found that BmPsc gene was widely expressed in all the tissues. Its expression level in gonad and ovary was the highest, followed by wing disc （containing hematopoietic organ）. It also had high expression level in circulated blood. The expression of BmPsc gene at different developmental periods of the 5th instar larvae had certain regularity. It reached the peak value at about day 2 of the 5th instar and day 6 of the 5th instar before metamorphosis, but was at the lowest level in middle of the 5th instar （day 4 to day 5）. The present study establishes a good basis for further investigations on inhibitory effect of BmPsc gene to stem cell differentiation at cellular level and

关 键 词：家蚕 多梳蛋白 BmPsc基因 序列特征 QRT-PCR 时空表达 

分 类 号：S881.2[农业科学—特种经济动物饲养] Q78[农业科学—畜牧兽医]