Wu Lizhen, Yadavalli Anurupa Devi, Matos-Rodrigues Gabriel, Xu Dijin, Pintado-Urbanc Andreas P, Simon Matthew D, Wu Wei, Nussenzweig André, Schatz David G
Department of Immunobiology, Yale School of Medicine, 300 Cedar Street, Box 208011, New Haven, CT 06520-8011, USA.
Laboratory of Genome Integrity, National Cancer Institute NIH, Bethesda, MD, USA.
bioRxiv. 2024 Sep 26:2024.09.24.614732. doi: 10.1101/2024.09.24.614732.
Somatic hypermutation (SHM) and class switch recombination (CSR) diversify immunoglobulin (Ig) genes and are initiated by the activation induced deaminase (AID), a single-stranded DNA cytidine deaminase that is thought to engage its substrate in the context of RNA polymerase II (RNAPII) transcription. Through a loss of function genetic screen, we identified numerous potential factors involved in SHM including ELOF1, a component of the RNAPII elongation complex that has been shown to function in DNA repair and transcription elongation. Loss of ELOF1 strongly compromises SHM, CSR, and AID targeting and alters RNAPII transcription by reducing RNAPII pausing downstream of transcription start sites and levels of serine 5 but not serine 2 phosphorylated RNAPII throughout transcribed genes. ELOF1 must bind to RNAPII to be a proximity partner for AID and to function in SHM and CSR. We propose that ELOF1 helps create the appropriate stalled RNAPII substrate on which AID acts.
体细胞高频突变（SHM）和类别转换重组（CSR）使免疫球蛋白（Ig）基因多样化，并由活化诱导的脱氨酶（AID）启动，AID是一种单链DNA胞嘧啶脱氨酶，被认为在RNA聚合酶II（RNAPII）转录的背景下与底物结合。通过功能丧失遗传筛选，我们鉴定出许多参与SHM的潜在因子，包括ELOF1，它是RNAPII延伸复合物的一个组分，已被证明在DNA修复和转录延伸中发挥作用。ELOF1的缺失严重损害SHM、CSR和AID靶向，并通过减少转录起始位点下游的RNAPII暂停以及整个转录基因中丝氨酸5而非丝氨酸2磷酸化的RNAPII水平来改变RNAPII转录。ELOF1必须与RNAPII结合才能成为AID的邻近伙伴并在SHM和CSR中发挥作用。我们提出，ELOF1有助于创建AID作用的合适停滞RNAPII底物。
