Cellular senescence induced by down-regulation of PTBP1 correlates with exon skipping of mitochondrial related gene NDUFV3

As the most prevalent type of alternative splicing in animal cells, exon skipping plays an important role in expanding the diversity of transcriptome and proteome, thereby participating the regulation of diverse physiological and pathological processes such as development, aging and cancer. Cellular senescence serves as an anti-cancer mechanism could also contribute to individual aging. Although the dynamic changes of exon skipping during cellular senescence were revealed, its biological consequence and upstream regulator remain poorly understood. Here, by using human foreskin fibroblasts (HFF) replicative senescence as a model, we discovered that splicing factor PTBP1 was an important contributor for global exon skipping events during senescence. Down-regulated expression of PTBP1 induced senescence-associated phenotypes and related mitochondrial functional changes. Mechanistically, PTBP1 binds to the third exon of mitochondrial complex I subunit coding gene NDUFV3 and protects the exon from skipping. We further confirmed that exon skipping of NDUFV3 correlates with and partially contributes to cellular senescence and related mitochondrial functional changes upon PTBP1 knockdown. Together, we revealed for the first time that mitochondrial related gene NDUFV3 is a new downstream target for PTBP1-regulated exon skipping to mediate cellular senescence and mitochondrial functional changes. Total RNA were isolated with TRIzol reagent according to manufacturer's instructions (Invitrogen, 15596026). Then, RNA was reversely transcribed into cDNA with oligo-(dT)23 VN primer and (or) random hexamers using HiScript II 1st Strand cDNA Synthesis Kit (+gDNA wiper) (Vazyme, R212). Gene expression at the RNA level was quantified by qRT-PCR using 2× SYBR mix (Vazyme, Q711). GAPDH’s RNA expression level served as an internal control.