RESUMEN
Xeroderma pigmentosum group D (XPD) protein is one of the subunits of TFIIH that is required for nucleotide excision repair and transcription. We found a XPD protein complex containing MMS19 that was assumed to be a regulator of TFIIH. However, the MMS19-XPD complex did not contain any other subunits of TFIIH. Instead, it included FAM96B (now designated MIP18), Ciao1, and ANT2. MMS19, MIP18, and XPD localized to the mitotic spindle during mitosis. The siRNA-mediated knockdown of MMS19, MIP18, or XPD led to improper chromosome segregation and the accumulation of nuclei with abnormal shapes. In addition, the frequency of abnormal mitosis and nuclei was increased in XP-D and XP-D/CS patients' cells. These results indicate that the MMS19-XPD protein complex, now designated MMXD (MMS19-MIP18-XPD), is required for proper chromosome segregation, an abnormality of which could contribute to the pathogenesis in some cases of XP-D and XP-D/CS.
Asunto(s)
Proteínas Portadoras/metabolismo , Segregación Cromosómica , Proteínas Nucleares/metabolismo , Factor de Transcripción TFIIH/metabolismo , Factores de Transcripción/metabolismo , Proteína de la Xerodermia Pigmentosa del Grupo D/metabolismo , Xerodermia Pigmentosa/genética , Translocador 2 del Nucleótido Adenina/metabolismo , Sitios de Unión , Proteínas Portadoras/genética , Forma del Núcleo Celular , Técnicas de Silenciamiento del Gen , Células HCT116 , Células HeLa , Humanos , Metalochaperonas/metabolismo , Metaloproteínas , Microscopía Fluorescente , Mitosis , Complejos Multiproteicos , Proteínas Nucleares/genética , Dominios y Motivos de Interacción de Proteínas , Mapeo de Interacción de Proteínas , Interferencia de ARN , Huso Acromático/metabolismo , Factores de Transcripción/genética , Transfección , Xerodermia Pigmentosa/metabolismo , Xerodermia Pigmentosa/patología , Proteína de la Xerodermia Pigmentosa del Grupo D/genéticaRESUMEN
XPG is a causative gene underlying the photosensitive disorder xeroderma pigmentosum group G (XP-G) and is involved in nucleotide excision repair. Here, we show that XPG knockdown represses epidermal growth factor (EGF)-induced FOS transcription at the level of transcription elongation with little effect on EGF signal transduction. XPG interacted with transcription elongation factors in concert with TFIIH, suggesting that the XPG-TFIIH complex serves as a transcription elongation factor. The XPG-TFIIH complex was recruited to promoter and coding regions of both EGF-induced (FOS) and housekeeping (EEF1A1) genes. Further, EGF-induced recruitment of RNA polymerase II and TFIIH to FOS was reduced by XPG knockdown. Importantly, EGF-induced FOS transcription was markedly lower in XP-G/Cockayne syndrome (CS) cells expressing truncated XPG than in control cells expressing wild-type (WT) XPG, with less significant decreases in XP-G cells with XPG nuclease domain mutations. In corroboration of this finding, both WT XPG and a missense XPG mutant from an XP-G patient were recruited to FOS upon EGF stimulation, but an XPG mutant mimicking a C-terminal truncation from an XP-G/CS patient was not. These results suggest that the XPG-TFIIH complex is involved in transcription elongation and that defects in this association may partly account for Cockayne syndrome in XP-G/CS patients.