Gallina A, Percivalle E, Simoncini L, Revello M G, Gerna G, Milanesi G
Instituto di Genetica Biochimica ed Evoluzionistica, Consiglio Nazionale delle Ricerche, Pavia, Italy.
J Gen Virol. 1996 Jun;77 ( Pt 6):1151-7. doi: 10.1099/0022-1317-77-6-1151.
Human cytomegalovirus phosphoprotein pp65 is targeted to the cell nucleus immediately after infection. Deletion and point mutation analysis of the pp65 gene expressed in insect cells showed that two hydrophilic regions (HP1 and HP2) within the pp65 C-terminal 40% each harboured an independent nuclear localization signal (NLS); strong association to the nuclear stroma also requires the N-terminal domain. Either region, when fused to chloramphenicol acetyltransferase, localized the reporter protein to the nucleus in insect cells as well as in NIH 3T3 cells and human lung fibroblasts. In addition, HP1 was found to be the target of pp65 Ser/Thr phosphorylation in insect cells and a prokaryotically expressed HP1 was actively phosphorylated in vitro by casein kinase II, for which two site clusters map in HP1. These findings indicate that pp65 includes two NLSs, one of which has the potential to be modulated by phosphorylation.
人巨细胞病毒磷蛋白pp65在感染后立即被转运至细胞核。对在昆虫细胞中表达的pp65基因进行缺失和点突变分析表明，pp65 C末端40%内的两个亲水区（HP1和HP2）各自含有一个独立的核定位信号（NLS）；与核基质的紧密结合也需要N末端结构域。当这两个区域中的任何一个与氯霉素乙酰转移酶融合时，均可将报告蛋白定位于昆虫细胞、NIH 3T3细胞及人肺成纤维细胞的细胞核中。此外，发现HP1是昆虫细胞中pp65丝氨酸/苏氨酸磷酸化的靶点，原核表达的HP1在体外可被酪蛋白激酶II活性磷酸化，HP1中有两个位点簇与之对应。这些发现表明，pp65包含两个NLS，其中一个有可能被磷酸化调节。
