Orstavik S, Eide T, Collas P, Han I O, Taskén K, Kieff E, Jahnsen T, Skålhegg B S
Institute of Medical Biochemistry, Faculty of Medicine, University of Oslo, Norway.
Biol Cell. 2000 Jan;92(1):27-37. doi: 10.1016/s0248-4900(00)88761-4.
Previously, we have identified and characterized nuclear AKAP95 from man which targets cyclic AMP (cAMP)-dependent protein kinase (PKA)-type II to the condensed chromatin/spindle region at mitosis. Here we report the cloning of a novel nuclear protein with an apparent molecular mass of 95 kDa that is similar to AKAP95 and is designated HA95 (homologous to AKAP95). HA95 cDNA sequence encodes a protein of 646 amino acids that shows 61% homology to the deduced amino acid sequence of AKAP95. The HA95 gene is located on chromosome 19p13.1 immediately upstream of the AKAP95 gene. Both HA95 and AKAP95 genes contain 14 exons encoding similar regions of the respective proteins, indicating a previous gene duplication event as the origin of the two tandem genes. Despite their apparent similarity, HA95 does not bind RII in vitro. HA95 contains a putative nuclear localization signal in its N-terminal domain. It is localized exclusively into the nucleus as demonstrated in cells transfected with HA95 fused to either green fluorescence protein or the c-myc epitope. In the nucleus, the HA95 protein is found as complexes directly associated with each other or indirectly associated via other nuclear proteins. In interphase, HA95 is co-localized with AKAP95, but the two proteins are not biochemically associated. At metaphase, both proteins co-localize with condensed chromosomes. The similarity in sequence and localization of HA95 and AKAP95 suggests that the two molecules constitute a novel family of nuclear proteins that may exhibit related functions.
此前，我们已从人类中鉴定并表征了核内的AKAP95，它在有丝分裂时将环磷酸腺苷（cAMP）依赖性蛋白激酶（PKA）II型靶向浓缩染色质/纺锤体区域。在此，我们报告克隆了一种新的核蛋白，其表观分子量为95 kDa，与AKAP95相似，被命名为HA95（与AKAP95同源）。HA95 cDNA序列编码一个由646个氨基酸组成的蛋白质，与AKAP95推导的氨基酸序列具有61%的同源性。HA95基因位于19号染色体p13.1上，紧挨着AKAP95基因的上游。HA95和AKAP95基因都包含14个外显子，编码各自蛋白质的相似区域，表明这两个串联基因起源于先前的基因复制事件。尽管它们明显相似，但HA95在体外不与RII结合。HA95在其N端结构域含有一个假定的核定位信号。如用与绿色荧光蛋白或c-myc表位融合的HA95转染细胞所证明的，它仅定位于细胞核。在细胞核中，HA95蛋白以直接相互关联或通过其他核蛋白间接关联的复合物形式存在。在间期，HA95与AKAP95共定位，但这两种蛋白在生化上不相关。在中期，这两种蛋白都与浓缩染色体共定位。HA95和AKAP95在序列和定位上的相似性表明，这两个分子构成了一个可能具有相关功能的新型核蛋白家族。
