Marzluff William F, Sakallah Sameer, Kelkar Hemant
Program in Molecular Biology and Biotechnology, University of North Carolina, Chapel Hill, NC 27599, USA.
Dev Biol. 2006 Dec 1;300(1):308-20. doi: 10.1016/j.ydbio.2006.08.067. Epub 2006 Sep 1.
The only eukaryotic mRNAs that are not polyadenylated are the replication-dependent histone mRNAs in metazoans. The sea urchin genome contains two sets of histone genes that encode non-polyadenylated mRNAs. One of these sets is a tandemly repeated gene cluster with a 5.6-kb repeat unit containing one copy of each of the five alpha-histone genes and is present as a single large cluster which spans over 1 Mb. There is a second set of genes, consisting of 39 genes, containing two histone H1 genes, 34 genes encoding core histone proteins (H2a, H2b, H3 and H4) and three genes expressed only in the testis. Unlike vertebrates where these genes are clustered, the sea urchin late histone genes, expressed in embryos, larvae and adults, are dispersed throughout the genome. There are also genes encoding polyadenylated histone mRNAs, which encode histone variants, including all variants found in other metazoans, as well as a unique set of five cleavage stage histone proteins expressed in oocytes. The cleavage stage histone H1 is the orthologue of an oocyte-specific histone H1 protein found in vertebrates.
后生动物中唯一未进行多聚腺苷酸化的真核生物mRNA是复制依赖型组蛋白mRNA。海胆基因组包含两组编码非多聚腺苷酸化mRNA的组蛋白基因。其中一组是串联重复的基因簇，其重复单元为5.6 kb，包含五个α-组蛋白基因中的每一个的一个拷贝，并且作为一个跨越超过1 Mb的单个大簇存在。还有第二组基因，由39个基因组成，包含两个组蛋白H1基因、34个编码核心组蛋白（H2a、H2b、H3和H4）的基因以及三个仅在睾丸中表达的基因。与这些基因成簇的脊椎动物不同，海胆中在胚胎、幼虫和成虫中表达的晚期组蛋白基因分散在整个基因组中。也有编码多聚腺苷酸化组蛋白mRNA的基因，其编码组蛋白变体，包括在其他后生动物中发现的所有变体，以及在卵母细胞中表达的一组独特的五个卵裂期组蛋白蛋白。卵裂期组蛋白H1是在脊椎动物中发现的卵母细胞特异性组蛋白H1蛋白的直系同源物。
