Ssb1 and Ssb2 have essential and overlapping functions in adult stem cell homeostasis - megakaryocyte-erythroid progenitor data.

The single-stranded DNA binding proteins SSB1 and SSB2 are crucial regulators of the DNA damage response, however the overlapping functions of these related proteins is incompletely understood. We generated mice where both Ssb1 and Ssb2 were constitutively or conditionally deleted. Constitutive Ssb1/Ssb2 double knockout (DKO) caused early embryonic lethality, while conditional Ssb1/Ssb2 double knockout (cDKO) in adult mice resulted in acute lethality due to bone marrow failure and intestinal atrophy featured by stem and progenitor cell depletion. cDKO cells exhibited increased replication stress, R-loop accumulation, genome wide double strand breaks and cytosolic single-stranded DNA. Transcriptional profiling of cDKO cells revealed activation of p53 DNA damage and interferon responses. Hematopoietic stem and progenitor cells in cDKO mice showed enforced cell cycling, with subsequent apoptotic cell death. Collectively, these results demonstrate that Ssb1 and Ssb2 have compensatory functions in maintaining genomic stability and are collectively necessary for adult stem cell homeostasis. Single colour, Illumina MouseRef-8 v2.0 Beadarrays.

单链DNA结合蛋白SSB1与SSB2是DNA损伤应答的关键调控因子，但目前对这两种相关蛋白的重叠功能尚未完全阐明。我们构建了可同时组成型或条件性敲除Ssb1与Ssb2的小鼠模型。组成型Ssb1/Ssb2双敲除（DKO）会引发胚胎早期致死；而成年小鼠体内的条件性Ssb1/Ssb2双敲除（cDKO）则会导致急性致死，其诱因包括骨髓衰竭与肠道萎缩，二者均以干细胞及祖细胞耗竭为特征。cDKO细胞表现出复制应激水平升高、R环（R-loop）积累、全基因组双链断裂以及胞质单链DNA蓄积。对cDKO细胞的转录谱分析显示，p53介导的DNA损伤应答与干扰素应答被激活。cDKO小鼠体内的造血干细胞及祖细胞出现细胞周期进程异常增强，随后发生凋亡性细胞死亡。综上，上述结果表明Ssb1与Ssb2在维持基因组稳定性过程中存在代偿功能，且二者共同为成体干细胞稳态所必需。本研究采用单色Illumina MouseRef-8 v2.0微珠芯片阵列进行检测。