DNA受到損傷後細胞會啟動後複製修復(post-replication repair, PRR) 機制來越過損傷，避免傷害加劇，而後複製修復下游又可以分為兩條子路徑，分別為跨損傷修復 (translesion synthesis, TLS)以及模板置換(template switching, TS)修復，其中TS路徑能藉由複製叉反轉 (fork reversal)來越過損傷。 在哺乳類動物中，HLTF與SHPRH被發現與酵母中參與TS路徑的Rad5互為同源基因並具有E3連接酶的活性，此前實驗室發表HLTF會參與在TS路徑中，但SHPRH的功能以及是否參與在TS路徑中目前尚未明瞭，因此本篇實驗的目標為確認SHPRH在TS路徑上的功能。
我們的研究結果發現，SHPRH能與TS修復路徑中的蛋白PARP1和BARD1進行交互作用，與先前實驗室研究的HLTF具有相似的功能。 我們進一步用免疫共沉澱實驗 (Co-IP)發現SHPRH (2-606)片段就能與PARP1有很好的交互作用。 在鼻咽癌細胞HONE1中將SHPRH表現量降低發現其對抗癌藥物4NQO的敏感度顯著提升。我們接著在HONE1細胞使用CRISPR-Cas9技術建立HLTF基因剔除的細胞株，在此細胞中抑制SHPRH的表現量對藥物的敏感度有更為顯著的提升。
染色體互換需要有雙股斷裂的發生以及Rad51參與股的入侵 (strand invasion)，根據實驗室先前研究發現HLTF缺失的細胞株會降低Rad51聚集在復製叉上的能力，造成姊妹染色分體互換 (SCE)的數量減少，在抑制SHPRH表現的細胞株中我們同樣發現SCE的數量減少，我們總結實驗後確認SHPRH在TS路徑中與HLTF具有相似的功能。

Post-replication repair (PRR) is a lesion bypass mechanism during DNA replication. One subpathway of PRR, known as template switching, bypasses DNA lesions by using the fork reversal mechanism. Previous studies have demonstrated that HLTF can promote the fork reversal structure in response to replication stress. SHPRH is a homologous gene of HLTF, which shares similar protein domain structure and E3 ligase activity. However, it remains unclear whether SHPRH has functions similar to HLTF in the TS pathway. Therefore, we aim to characterize the function of SHPRH in the TS pathway in this study. Here, we found that SHPRH interacts with PARP1 and BARD1, similar to the biochemical function of HLTF. We further map the N-terminal domain of SHPRH (2-606) interacts with PARP1. The depletion of SHPRH sensitizes cells to DNA damaging agent 4NQO. We also generated the HLTF knockout cells by using the CRISPR gene knockout strategy. The depletion of SHPRH further sensitizes the HLTF knockout cells to DNA damaging agents. Previously, we found that the depletion of HLTF decreases the level of RAD51 at stalled forks and the frequency of sister chromatid exchange (SCE). Similarly, we found the depletion of SHPRH also deceases the frequency of SCE. We conclude that SHPRH has functions similar to HLTF in the TS pathway.

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