Identification, cloning and characterization of a novel nuclear protein, HA95, homologous to A-kinase anchoring protein 95

Previously, we have identified and characterized nuclear AKAP95 from man wh ich 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 i s similar to AKAP95 and is designated HA95 (homologous to AKAP95). HA95 cDN A 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 chro mosome 19p13.1 immediately upstream of the AKAP95 gene. Both HA95 and AKAP9 5 genes contain 14 exons encoding similar regions of the respective protein s, indicating a previous gene duplication event as the origin of the two ta ndem genes. Despite their apparent similarity, HA95 does not bind RII in vi tro. HA95 contains a putative nuclear localization signal in its N-terminal domain. It is localized exclusively into the nucleus as demonstrated in ce lls transfected with HA95 fused to either green fluorescence protein or the c-myc epitope. In the nucleus, the HA95 protein is found as complexes dire ctly associated with each other or indirectly associated via other nuclear proteins. In interphase, HA95 is co-localized with AKAP95, but the two prot eins are not biochemically associated. At metaphase, both proteins co-local ize with condensed chromosomes. The similarity in sequence and localization of HA95 and AKAP95 suggests that the two molecules constitute a novel fami ly of nuclear proteins that may exhibit related functions. 2000 (C) Edition s scientifiques et medicales Elsevier SAS.