MOLECULAR MECHANISM OF TRANSCRIPTION-REPAIR COUPLING
MOLECULAR MECHANISM OF TRANSCRIPTION-REPAIR COUPLING
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DOI：
10.1126/science.8465200
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发表时间：
1993-04-02
期刊：
影响因子：
56.9
通讯作者：
SANCAR, A
中科院分区：
文献类型：
--
作者：
SELBY, CP;SANCAR, A
转录链中的损伤阻断转录，并且比不阻断RNA聚合酶（RNAP）的非转录（编码）链中的损伤更快地修复。以前已经表明，在大肠杆菌中，mfd（突变频率下降）基因是链特异性修复所必需的。对mfd基因进行了克隆和测序，并纯化了Mfd蛋白，用于在完全确定的系统中重建链特异性修复。mfd基因编码一种130千道尔顿的蛋白质，包含所谓的“解旋酶基序”、亮氨酸拉链基序以及与UvrB和RecG蛋白质序列相似的区域。Mfd蛋白被证明（i）在三磷酸腺苷依赖性反应中取代在损伤处停滞的RNAP，（ii）结合切除核酸酶的损伤识别亚基（UvrA），以及（iii）仅当转录发生时刺激转录链的修复。因此，Mfd似乎通过识别停滞的RNAP并在其解离停滞的RNAP时主动将修复酶募集到转录阻断损伤来靶向转录链进行修复。
Lesions in the transcribed strand block transcription and are repaired more rapidly than lesions in the nontranscribed (coding) strand which do not block RNA polymerase (RNAP). It has been shown previously that in Escherichia coli the mfd (mutation frequency decline) gene is necessary for strand-specific repair. The mfd gene was cloned and sequenced and the Mfd protein was purified and used to reconstitute strand-specific repair in a completely defined system. The mfd gene encodes a protein of 130 kilodaltons and contains the so-called ''helicase motifs,'' a leucine zipper motif, and regions of sequence similarity to UvrB and RecG proteins. The Mfd protein was shown to (i) displace RNAP stalled at a lesion in an adenosine triphosphate-dependent reaction, (ii) bind to the damage recognition subunit (UvrA) of the excision nuclease, and (iii) stimulate the repair of the transcribed strand only when transcription is taking place. Thus, Mfd appears to target the transcribed strand for repair by recognizing a stalled RNAP and actively recruiting the repair enzyme to the transcription blocking lesion as it dissociates the stalled RNAP.