Elf1 promotes Rad26's interaction with lesion-arrested Pol II for transcription-coupled repair

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• Transcription-coupled nucleotide excision repair (TC-NER) removes DNA lesions from transcribed regions.
• Cockayne syndrome B protein (CSB) and its yeast ortholog Rad26 are crucial for TC-NER lesion recognition.
• ELOF1 and its yeast ortholog Elf1 are newly identified core TC-NER factors.

Purpose of the Study:

• To elucidate the mechanism by which Rad26 distinguishes stalled RNA polymerase II (Pol II) at DNA lesions versus other obstacles.
• To determine the role of Elf1 in the Rad26-mediated lesion recognition process within TC-NER.

Main Methods:

• Cryo-electron microscopy (cryo-EM) to determine structures of Pol II-Rad26 complexes stalled at various obstacles.
• Cryo-EM to visualize the lesion-arrested Pol II-Rad26-Elf1 complex.
• Biochemical and genetic assays to validate the functional significance of Elf1-Rad26 interactions.

Main Results:

• Cryo-EM structures reveal Rad26 employs a common mechanism for stalled Pol II recognition, with specific adaptations for lesion-induced arrest.
• The structure of the lesion-arrested Pol II-Rad26-Elf1 complex shows Elf1 enhances Rad26 interactions with the arrested Pol II.
• Biochemical and genetic data confirm the essential interplay between Elf1 and Rad26 for TC-NER initiation.

Conclusions:

• Rad26 and Elf1 cooperate through specific interactions to initiate TC-NER by recognizing DNA lesions stalled by Pol II.
• These findings provide critical mechanistic insights into the early steps of TC-NER involving conserved repair factors.