Department of Biochemistry and Biophysics, University of Rochester School of Medicine and Dentistry, Rochester, NY 14642, USA.
Nucleic Acids Res. 2010 Jan;38(3):920-30. doi: 10.1093/nar/gkp1055. Epub 2009 Nov 24.
Dna2 is a nuclease/helicase with proposed roles in DNA replication, double-strand break repair and telomere maintenance. For each role Dna2 is proposed to process DNA substrates with a 5'-flap. To date, however, Dna2 has not revealed a preference for binding or cleavage of flaps over single-stranded DNA. Using DNA binding competition assays we found that Dna2 has substrate structure specificity. The nuclease displayed a strong preference for binding substrates with a 5'-flap or some variations of flap structure. Further analysis revealed that Dna2 recognized and bound both the single-stranded flap and portions of the duplex region immediately downstream of the flap. A model is proposed in which Dna2 first binds to a flap base, and then the flap threads through the protein with periodic cleavage, to a terminal flap length of approximately 5 nt. This resembles the mechanism of flap endonuclease 1, consistent with cooperation of these two proteins in flap processing.
Dna2 是一种核酸酶/解旋酶，据推测在 DNA 复制、双链断裂修复和端粒维持中发挥作用。对于每个作用，Dna2 都被提议处理具有 5'-flap 的 DNA 底物。然而，到目前为止，Dna2 尚未表现出对结合或切割 flap 与单链 DNA 的偏好。通过 DNA 结合竞争测定，我们发现 Dna2 具有底物结构特异性。该核酸酶强烈倾向于结合具有 5'-flap 或 flap 结构某些变体的底物。进一步的分析表明，Dna2 识别并结合单链 flap 以及 flap 下游的双链区域的部分区域。提出了一个模型，其中 Dna2 首先结合 flap 碱基，然后 flap 以周期性切割的方式穿过蛋白质，直到 flap 的末端长度约为 5nt。这类似于 flap 内切酶 1 的机制，与这两种蛋白质在 flap 加工中的合作一致。
