CDKN1B and infection: The stabilities of p21 and p27 proteins in HeLa-G and its ΔN-I-κBα progenies L6 and H5 were similar after infection with the control Ad-tTa vector, (Fig. 4A) suggesting that NF-κB in HeLa-G cells was already regulated by endogenous I-κBα, additional blocking of NF-κB with ΔN-I-κBα did not alter the levels of p21 and p27.