Chan J C, Scanlon M, Denhardt D T, Singh K, Mukherjee B B, Farach-Carson M C, Butler W T
University of Texas M.D. Anderson Cancer Center, Houston 77030.
Int J Cancer. 1990 Nov 15;46(5):864-70. doi: 10.1002/ijc.2910460519.
Transformation-associated protein (TAP) has been detected in MSV-M-transformed rat cell lines as glycosylated, weakly phosphorylated protein of molecular weight (Mr) 66,000 and 68,000. In the ts-MSV-M-transformed rat kidney cell line (6m2), the synthesis of TAP and the v-mos gene product is temperature-sensitive and accompanies the expression of transformation phenotypes. Therefore, TAP potentially plays a role in cellular transformation. On the other hand, SPP represents a family of glycosylated phosphoprotein with apparent Mr ranging from 42,000 to 69,000. SPP has been detected in osteoblasts and in avian and murine retrovirus-transformed rat and mouse epithelial cells. Therefore, the potential relatedness of TAP and SPP was studied. Using the 6m2 cells, we found that SPP was strongly phosphorylated and was synthesized at both the permissive (33 degrees C) and non-permissive (39 degrees C) temperatures. By contrast, TAP was weakly phosphorylated, and was synthesized, as we found previously, only at the permissive temperature of 33 degrees C. Furthermore, in 35S-methionine incorporation studies, TAP became heavily labelled whereas SPP was not (consistent with its amino acid composition having few methionine residues). Using 125I-TAP in both immunoprecipitation and radioimmunoassays, it was found that an antiserum raised against SPP did not cross-react with 125I-TAP. Additionally, SPP has now been found in many human and rodent cells, while TAP thus far has only been detected in MSV-transformed rat cells. These data suggest that structurally, TAP and SPP are not closely related phosphoproteins.
在MSV-M转化的大鼠细胞系中已检测到转化相关蛋白（TAP），它是一种糖基化、弱磷酸化的蛋白质，分子量（Mr）分别为66,000和68,000。在ts-MSV-M转化的大鼠肾细胞系（6m2）中，TAP和v-mos基因产物的合成对温度敏感，并伴随着转化表型的表达。因此，TAP可能在细胞转化中发挥作用。另一方面，SPP代表一类糖基化磷蛋白家族，其表观Mr范围为42,000至69,000。已在成骨细胞以及禽和鼠逆转录病毒转化的大鼠和小鼠上皮细胞中检测到SPP。因此，对TAP和SPP的潜在相关性进行了研究。使用6m2细胞，我们发现SPP被强烈磷酸化，并且在允许温度（33℃）和非允许温度（39℃）下均能合成。相比之下，TAP磷酸化程度较弱，并且正如我们之前发现的，仅在33℃的允许温度下合成。此外，在35S-甲硫氨酸掺入研究中，TAP被大量标记，而SPP没有（这与其氨基酸组成中蛋氨酸残基较少一致）。在免疫沉淀和放射免疫测定中使用125I-TAP，发现针对SPP产生的抗血清与125I-TAP不发生交叉反应。此外，现在已在许多人类和啮齿动物细胞中发现了SPP，而迄今为止仅在MSV转化的大鼠细胞中检测到TAP。这些数据表明，在结构上，TAP和SPP不是密切相关的磷蛋白。
