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Background: It is unknown whether SENP1 controls adipocyte differentiation. Results: SENP1 de-SUMOylates Sharp-1 and promotes PPAR␥ expression and adipogenesis. Conclusion: SENP1 regulates adipocyte differentiation. Significance: SENP1 is a novel regulator in adipocyte differentiation.

Background: It was unknown whether human ␤-arrestin 2 could be SUMOylated. Results: Human ␤-arrestin 2 is SUMOylated on Lys-295. SUMOylation attenuates ␤-arrestin 2 inhibition of IL-1R/TRAF6 signaling. Conclusion: SUMOylation attenuates human ␤-arrestin 2 inhibition of TRAF6 and IL-1R signaling. Significance: We show SUMOylation as a novel mechanism in regulation of ␤-arrestin 2-mediated IL-1R-TRAF6 signaling.

Expression of wild-type protein tyrosine phosphatase (PTP) 1B may act either as a tumor suppressor by dysregulation of protein tyrosine kinases or a tumor promoter through Src dephosphorylation at Y527 in human breast cancer cells. To explore whether mutated PTP1B is involved in human carcinogenesis, we have sequenced PTP1B cDNAs from human tumors and found splice mutations in ~20% of colon and thyroid tumors. The PTP1BΔE6 mutant expressed in these two tumor types and another PTP1BΔE5 mutant expressed in colon tumor were studied in more detail. Although PTP1BΔE6 revealed no phosphatase activity compared with wild-type PTP1B and the PTP1BΔE5 mutant, its expression induced oncogenic transformation of rat fibroblasts without Src activation, indicating that it involved signaling pathways independent of Src. The transformed cells were tumourigenic in nude mice, suggesting that the PTP1BΔE6 affected other molecule(s) in the human tumors. These observations may provide a novel therapeutic target for colon and thyroid cancer.