Institute for Molecular Virology and McArdle Laboratory for Cancer Research, University of Wisconsin-Madison, Madison, Wisconsin, United States of America.
PLoS Pathog. 2024 Sep 5;20(9):e1012516. doi: 10.1371/journal.ppat.1012516. eCollection 2024 Sep.
ATRX limits the accumulation of human cytomegalovirus (HCMV) Immediate Early (IE) proteins at the start of productive, lytic infections, and thus is a part of the cell-intrinsic defenses against infecting viruses. ATRX is a chromatin remodeler and a component of a histone chaperone complex. Therefore, we hypothesized ATRX would inhibit the transcription of HCMV IE genes by increasing viral genome heterochromatinization and decreasing its accessibility. To test this hypothesis, we quantitated viral transcription and genome structure in cells replete with or depleted of ATRX. We found ATRX did indeed limit viral IE transcription, increase viral genome chromatinization, and decrease viral genome accessibility. The inhibitory effects of ATRX extended to Early (E) and Late (L) viral protein accumulation, viral DNA replication, and progeny virion output. However, we found the negative effects of ATRX on HCMV viral DNA replication were independent of its effects on viral IE and E protein accumulation but correlated with viral genome heterochromatinization. Interestingly, the increased number of viral genomes synthesized in ATRX-depleted cells were not efficiently packaged, indicating the ATRX-mediated restriction to HCMV viral DNA replication may benefit productive infection by increasing viral fitness. Our work mechanistically describes the antiviral function of ATRX and introduces a novel, pro-viral role for this protein, perhaps explaining why, unlike during infections with other herpesviruses, it is not directly targeted by a viral countermeasure in HCMV infected cells.
ATRX 限制了人巨细胞病毒 (HCMV) 立即早期 (IE) 蛋白在产生活性裂解感染时的积累，因此是细胞固有防御感染病毒的一部分。ATRX 是一种染色质重塑酶，也是组蛋白伴侣复合物的组成部分。因此，我们假设 ATRX 通过增加病毒基因组异染色质化和降低其可及性来抑制 HCMV IE 基因的转录。为了验证这一假设，我们在富含或耗尽 ATRX 的细胞中定量检测了病毒转录和基因组结构。我们发现 ATRX 确实限制了病毒 IE 转录，增加了病毒基因组染色质化，并降低了病毒基因组的可及性。ATRX 的抑制作用延伸至早期 (E) 和晚期 (L) 病毒蛋白积累、病毒 DNA 复制和子代病毒粒子产量。然而，我们发现 ATRX 对 HCMV 病毒 DNA 复制的负效应与其对病毒 IE 和 E 蛋白积累的影响无关，但与病毒基因组异染色质化相关。有趣的是，在 ATRX 耗尽的细胞中合成的大量病毒基因组并未被有效包装，这表明 ATRX 介导的对 HCMV 病毒 DNA 复制的限制可能通过增加病毒适应性而有益于产生活性感染。我们的工作从机制上描述了 ATRX 的抗病毒功能，并引入了这种蛋白质的一种新的、促进病毒的作用，这也许可以解释为什么与其他疱疹病毒感染不同，ATRX 不会成为 HCMV 感染细胞中病毒反制措施的直接靶标。
