Transglutaminase 2 inhibits Rb binding of human papillomavirus E7 by incorporating polyamine.
Transglutaminase 2 (TGase 2) is one of a family of enzymes that catalyze protein modification through the incorporation of polyamines into substrates or the formation of protein crosslinks. However, the physiological roles of TGase 2 are largely unknown. To elucidate the functions of TGase 2, we have searched for its interacting proteins. Here we show that TGase 2 interacts with E7 oncoprotein of human papillomavirus type 18 (HPV18) in vitro and in vivo. TGase 2 incorporates polyamines into a conserved glutamine residue in the zinc-binding domain of HPV18 E7 protein. This modification mediates the inhibition of E7's Rb binding ability. In contrast, TGase 2 does not affect HPV16 E7, due to absence of a glutamine residue at this polyamination site. Using E7 mutants, we demonstrate that TGase 2-dependent inhibition of HPV E7 function correlates with the presence of the polyamination site. Our results indicate that TGase 2 is an important cellular interfering factor and define a novel host-virus interaction, suggesting that the inability of TGase 2 to inactivate HPV16 E7 could explain the high prevalence of HPV16 in cervical cancer.
D004268:DNA-Binding Proteins; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006801:Humans; D009856:Oncogene Proteins, Viral / Q000378:metabolism*; D050725:Papillomavirus E7 Proteins; D011073:Polyamines / Q000378:metabolism*; D000091345:Protein Glutamine gamma Glutamyltransferase 2; D016160:Retinoblastoma Protein / Q000378:metabolism*; D011503:Transglutaminases / Q000378:metabolism*
D004268:DNA-Binding Proteins; C052633:E7 protein, Human papillomavirus type 18; D009856:Oncogene Proteins, Viral; D050725:Papillomavirus E7 Proteins; D011073:Polyamines; D016160:Retinoblastoma Protein; C059731:oncogene protein E7, Human papillomavirus type 16; D000091345:Protein Glutamine gamma Glutamyltransferase 2; D011503:Transglutaminases; D019204:GTP-Binding Proteins