Crystal Structure of the Rad3/XPD Regulatory Domain of Ssl1/p44

• Published in: The Journal of biological chemistry 2015-03, Vol.290 (13), p.8321-8330
• Main Authors: Kim, Jin Seok, Saint-André, Charlotte, Lim, Hye Seong, Hwang, Cheol-Sang, Egly, Jean Marc, Cho, Yunje
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Crystal Structure; Crystallography, X-Ray; DNA and Chromosomes; DNA Helicases - chemistry; DNA Repair; Models, Molecular; Molecular Sequence Data; Mutation, Missense; Nucleotide Excision Repair; Protein Binding; Protein Interaction Domains and Motifs; Protein Structure, Secondary; Rad3/XPD Helicase; Regulatory Domain of Ssl1/p44; Saccharomyces cerevisiae - metabolism; Saccharomyces cerevisiae Proteins - chemistry; Saccharomyces cerevisiae Proteins - genetics; Saccharomyces cerevisiae Proteins - metabolism; TFIIH; Transcription; Transcription Factor TFIIH - chemistry; Transcription Factor TFIIH - genetics; Transcription Factor TFIIH - metabolism; Yeast Genetics
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M115.636514

The Ssl1/p44 subunit is a core component of the yeast/mammalian general transcription factor TFIIH, which is involved in transcription and DNA repair. Ssl1/p44 binds to and stimulates the Rad3/XPD helicase activity of TFIIH. To understand the helicase stimulatory mechanism of Ssl1/p44, we determined the crystal structure of the N-terminal regulatory domain of Ssl1 from Saccharomyces cerevisiae. Ssl1 forms a von Willebrand factor A fold in which a central six-stranded β-sheet is sandwiched between three α helices on both sides. Structural and biochemical analyses of Ssl1/p44 revealed that the β4-α5 loop, which is frequently found at the interface between von Willebrand factor A family proteins and cellular counterparts, is critical for the stimulation of Rad3/XPD. Yeast genetics analyses showed that double mutation of Leu-239 and Ser-240 in the β4-α5 loop of Ssl1 leads to lethality of a yeast strain, demonstrating the importance of the Rad3-Ssl1 interactions to cell viability. Here, we provide a structural model for the Rad3/XPD-Ssl1/p44 complex and insights into how the binding of Ssl1/p44 contributes to the helicase activity of Rad3/XPD and cell viability. Background: Ssl1/p44 is a critical helicase stimulating factor for Rad3/XPD. Results: Structure-based mutation analysis of the β4-α5 loop of Ssl1/p44 resulted in defects of Rad3/XPD stimulation and yeast cell lethality. Conclusion: The β4-α5 loop of Ssl1/p44 is essential for the functional regulation of Rad3/XPD. Significance: These findings provide insights into the interaction between Rad3/XPD and Ssl1/p44 in TFIIH complex.