XPD Helicase (3CRV)
From Proteopedia
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== Function == | == Function == | ||
| - | XPD helicase is an essential subunit of the general transcription factor IIH (TFIIH), which is a complex that, along with other general transcription factors, helps to initiate transcription and repair damaged DNA <ref name="Mydikova">PMID: 20429618</ref>. XPD helicase helps to stabilize the structure of TFIIH but also plays a functional role in repairing DNA as a helicase enzyme <ref name="Lifuss">PMID: 18510924 </ref>. Helicases are enzymes that unwind double-stranded DNA into single-stranded DNA so that other enzymes, like polymerases, can act upon the DNA <ref name="Tuteja">PMID: 15128295 </ref>. In the context of DNA repair, helicases unwind DNA and other enzymes remove the damaged DNA and replace it with the complementary nucleotides based on the other DNA sequence. When DNA is exposed to UV radiation, adjacent nucleotide bases, often thymines, can react and form bulky pyrimidine dimers, which can block enzymes that work on DNA <ref name="Vink">PMID: 11809365 </ref>. For example, during DNA replication, thymine dimers do not fit into the active site of DNA polymerases smoothly, sometimes resulting in mismatched nucleotides. To fix this type of damage on single strands of DNA, cells employ a process called nucleotide excision repair (NER) <ref name="Lifuss">PMID: 18510924 </ref>. This is the type of DNA repair that TFIIH, with the help of the XPD helicase subunit, carries out to remove the damaged DNA. | + | XPD helicase is an essential subunit of the general transcription factor IIH (TFIIH), which is a complex that, along with other general transcription factors, helps to initiate transcription and repair damaged DNA <ref name="Mydikova">PMID: 20429618</ref>. XPD helicase helps to stabilize the structure of TFIIH but also plays a functional role in repairing DNA as a helicase enzyme <ref name="Lifuss">PMID: 18510924 </ref>. Helicases are enzymes that unwind double-stranded DNA into single-stranded DNA so that other enzymes, like polymerases, can act upon the DNA <ref name="Tuteja">PMID: 15128295 </ref>. In the context of DNA repair, helicases unwind DNA and other enzymes remove the damaged DNA and replace it with the complementary nucleotides based on the other DNA sequence. When DNA is exposed to UV radiation, adjacent nucleotide bases, often thymines, can react and form bulky pyrimidine dimers, which can block enzymes that work on DNA <ref name="Vink">PMID: 11809365 </ref>. For example, during DNA replication, [http://proteopedia.org/wiki/index.php/Category:Thymine_Dimers thymine dimers] do not fit into the active site of DNA polymerases smoothly, sometimes resulting in mismatched nucleotides. To fix this type of damage on single strands of DNA, cells employ a process called [http://proteopedia.org/wiki/index.php/Category:Nucleotide_excision_repair nucleotide excision repair (NER)] <ref name="Lifuss">PMID: 18510924 </ref>. This is the type of DNA repair that TFIIH, with the help of the XPD helicase subunit, carries out to remove the damaged DNA. |
Breaking the hydrogen bonds that hold the two DNA strands together requires energy, so XPD helicase is dependent on ATP <ref name="Buechner">PMID: 24338567 </ref>. The ATP-dependent helicase activity of XPD helicase, however is only required for NER, even though TFIIH participates in both repair and transcription initiation <ref name="Kuper">PMID: 25268380 </ref>. XPD helicase not only unravels the DNA around the damage, but also helps TFIIH in recognizing bulky lesions in DNA <ref>DOI 10.1093/nar/gkw102 </ref>. The DNA is then threaded through the central pore of XPD helicase, which then opens up the double helix. | Breaking the hydrogen bonds that hold the two DNA strands together requires energy, so XPD helicase is dependent on ATP <ref name="Buechner">PMID: 24338567 </ref>. The ATP-dependent helicase activity of XPD helicase, however is only required for NER, even though TFIIH participates in both repair and transcription initiation <ref name="Kuper">PMID: 25268380 </ref>. XPD helicase not only unravels the DNA around the damage, but also helps TFIIH in recognizing bulky lesions in DNA <ref>DOI 10.1093/nar/gkw102 </ref>. The DNA is then threaded through the central pore of XPD helicase, which then opens up the double helix. | ||
Revision as of 00:56, 27 April 2016
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