Pandey V N, Dave V P, Patil M S
Biochemistry Division, Bhabha Atomic Research Centre, Bombay, India.
Mol Biol Rep. 1988;13(4):179-84. doi: 10.1007/BF00788168.
Approximately 80% of the terminal deoxynucleotidyl transferase (TdT) in thymus glands from 3-4 week old rats was found to be localized in the nucleus and the remaining 20% in the cytosol. Following endogenous nuclease digestion of the thymus nuclei, 70-85% of the nuclear TdT could be removed by low salt and high salt extractions, whereas 15-30% of the enzyme remained tightly bound to the residual nuclear matrix. Low salt and high salt extracts of the nuclei contained a mixture of 58, 56, 45 and 44 kDa species of TdT whereas only 58 kDa species of the enzyme was found to be associated with the matrix. In addition to TdT, 20-25% of the nuclear DNA polymerase alpha was also tightly bound to the isolated nuclear matrix. These observations lead us to propose that besides being the site of DNA replication via-matrix bound replicational complexes [Van der Velden H.M.W. & Wanka F., Molecular Biology Reports 12 (1987): 69], nuclear matrix may also be the site of TdT mediated function and that matrix bound TdT and free TdT could be the functional and nonfunctional forms of the enzyme, respectively, in the thymus gland.
在3 - 4周龄大鼠的胸腺中，约80%的末端脱氧核苷酸转移酶（TdT）定位于细胞核，其余20%定位于细胞质。在对胸腺细胞核进行内源性核酸酶消化后，70 - 85%的核TdT可通过低盐和高盐提取去除，而15 - 30%的酶仍紧密结合于残留的核基质。细胞核的低盐和高盐提取物中含有58、56、45和44 kDa的TdT混合物，而仅发现58 kDa的酶与基质相关。除了TdT，20 - 25%的核DNA聚合酶α也紧密结合于分离的核基质。这些观察结果使我们提出，除了作为通过基质结合的复制复合物进行DNA复制的场所[Van der Velden H.M.W. & Wanka F., Molecular Biology Reports 12 (1987): 69]外，核基质也可能是TdT介导功能的场所，并且结合于基质的TdT和游离的TdT可能分别是胸腺中该酶的功能形式和非功能形式。
