RETRACTED: Siah-1 facilitates ubiquitination and degradation of factor inhibiting HIF-1α (FIH)

This article has been retracted at the request of the Editor-in-Chief and Author. Please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy).Reason: The authors have found that they are unable to reproduce some of the experiments. The authors re-examined the siRNA experiments used for Figure 4B and found that the data as reported in this figure cannot be relied upon. Since Siah-1 itself is rapidly degraded via the ubiquitin-proteasome system, the physiological expression level of Siah-1 is very low, and sometimes it is hard to detect by Western blotting even under normal cell culture conditions. Therefore, it is not clear how much endogenous Siah-1 contributes to FIH degradation.Careful quantitative analysis of Siah-1 siRNA experiments, such as evaluation of FIH protein/Siah-1 protein ratio, and reinvestigation is required. In technical issues, cell culture condition that increases endogenous Siah-1 expression should be also investigated. On the other hand, repeated Siah-1 transfection/overexpression experiments confirmed that “exogenously introduced” Siah-1 facilitates ubiquitination and degradation of FIH, but further investigation is required as to whether or not endogenous Siah-1 really facilitates degradation of endogenous FIH under physiological conditions. The authors would like to apologize for this error.