Whole genome expression data comparison between WT and Cebpg-/- MEFs.

C/EBP is an important regulator of oncogene-induced senescence (OIS). Here we show that C/EBP, a heterodimeric partner of C/EBP whose biological functions are not well understood, inhibits cellular senescence. Cebpg-/- MEFs proliferated poorly, entered senescence prematurely, and expressed a pro-inflammatory gene signature, including elevated levels of senescence-associated secretory phenotype (SASP) genes whose induction by oncogenic stress requires C/EBP. The senescence-suppressing activity of C/EBP required its ability to heterodimerize with C/EBP. Covalently linked C/EBP homodimers (~) inhibited the proliferation and tumorigenicity of RasV12-transformed NIH3T3 cells, activated SASP gene expression, and recruited the CBP co-activator in a Ras-dependent manner, whereas ~ heterodimers lacked these capabilities and efficiently rescued proliferation of Cebpg-/- MEFs. C/EBP depletion partially restored growth of C/EBP-deficient cells, indicating that the increased levels of C/EBP homodimers in Cebpg-/- MEFs inhibit proliferation. The proliferative functions of C/EBP are not restricted to fibroblasts, as hematopoietic progenitors from Cebpg-/- bone marrow also displayed impaired growth. Furthermore, high CEBPG expression correlated with poorer clinical prognoses in several human cancers, and C/EBP depletion decreased proliferation and induced senescence in lung tumor cells. Our findings demonstrate that C/EBP neutralizes the cytostatic activity of C/EBP through heterodimerization, which prevents senescence and suppresses basal transcription of SASP genes.

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Huggins CJ, Malik R, Lee S, Salotti J, Thomas S, Martin N, Quiñones OA, Alvord WG, Olanich ME, Keller JR, Johnson PF