Monday, August 25, 2014

Normal function of the XPB/ERCC3 gene

The ERCC3 gene helps in making a protein called XPB. XPB is an essential subunit of a group of proteins known as the general transcription factor IIH (TFIIH) complex. The TFIIH complex has two major functions:

          I.      It involves in a process of gene transcription
        II.      It helps repair damaged DNA.

Gene transcription is the first step in protein production. By controlling gene transcription, the TFIIH complex helps regulate the activity of many different genes. Research suggest that the XPB protein works together with XPD, another protein in the TFIIH complex that is produced from the ERCC2 gene, to initiate gene transcription.

The TFIIH complex also plays an important role in repairing damaged DNA, which can be damaged by ultraviolet (UV) rays from the sun and by toxic chemicals, radiation and unstable molecules called free radicals. As we already know that DNA damage occurs frequently, but normal cells usually fix the damage through nucleotide excision repair (NER) mechanism before it can cause problems. As part of this repair mechanism, the TFIIH complex unwinds the section of double-stranded DNA that surrounds the damage. Studies suggest that the XPB protein may act as a wedge, holding open the two strands of DNA so other proteins can snip out (excise) the abnormal section and replace the damaged area with the correct DNA.

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