Department of Chemistry, University of Utah, 315 South 1400 East, Salt Lake City, Utah 84112-0850, USA.
Biochemistry. 2010 Mar 2;49(8):1658-66. doi: 10.1021/bi901852q.
Human DNA glycosylase NEIL1 exhibits a superior ability to remove oxidized guanine lesions guanidinohydantoin (Gh) and spiroiminodihydantoin (Sp) from duplex DNA in comparison to other substrates. In this work, Gh and Sp lesions in bubble, bulge, and single-stranded DNA were found to be good substrates for NEIL1 but were typically excised at much slower rates than from canonical duplex substrates. A notable exception was the activity of NEIL1 on removal of Gh in bubble structures which approaches that of the normal duplex substrate. The cleavage of Gh in the template strand of a replication or transcription bubble may prevent mutations associated with Gh during replication or transcription. However, removal of hydantoin lesions in the absence of an opposite base may also result in strand breaks and potentially deletion and frameshift mutations. Consistent with this as a potential mechanism leading to an N-1 frameshift mutation, the nick left after the removal of the Gh lesion in a DNA bulge by NEIL1 was efficiently religated in the presence of polynucleotide kinase (PNK) and human DNA ligase III (Lig III). These results indicate that NEIL1 does not require a base opposite to identify and remove hydantoin lesions. Depending on the context, the glycosylase activity of NEIL1 may stall replication and prevent mutations or lead to inappropriate removal that may contribute to the mutational spectrum of these unusual lesions.
人类 DNA 糖苷酶 NEIL1 相较于其他底物，能够更有效地从双链 DNA 中去除氧化鸟嘌呤损伤鸟嘌呤脒基嘧啶酮（Gh）和螺环亚氨基二氢嘧啶酮（Sp）。在这项工作中，发现 Gh 和 Sp 损伤在泡状、膨出和单链 DNA 中是 NEIL1 的良好底物，但通常比从典型的双链底物中切除的速度要慢得多。一个值得注意的例外是 NEIL1 在去除泡状结构中的 Gh 活性，其接近正常双链底物的活性。复制或转录泡中模板链上 Gh 的切割可能会阻止与 Gh 相关的突变。然而，在没有相反碱基的情况下去除嘧啶酮损伤也可能导致链断裂，并可能导致缺失和移码突变。作为导致 N-1 移码突变的潜在机制，NEIL1 在 DNA 膨出处去除 Gh 损伤后留下的缺口在多核苷酸激酶（PNK）和人 DNA 连接酶 III（Lig III）存在的情况下能够有效重新连接。这些结果表明，NEIL1 不需要识别和去除嘧啶酮损伤的相反碱基。根据上下文，NEIL1 的糖苷酶活性可能会使复制停滞，防止突变，或导致不适当的去除，这可能导致这些异常损伤的突变谱。
