Transcription elongation factor ELOF1 is required for efficient somatic hypermutation and class switch recombination

Area of Science:

• Immunology
• Molecular Biology
• Genetics

Background:

• Somatic hypermutation (SHM) and class switch recombination (CSR) are essential processes for diversifying immunoglobulin (Ig) genes.
• These processes are initiated by activation-induced deaminase (AID), a DNA cytidine deaminase.
• AID is believed to interact with its DNA substrate during RNA polymerase II (RNAPII) transcription.

Purpose of the Study:

• To identify novel factors involved in SHM using a loss-of-function genetic screen.
• To investigate the role of ELOF1, a component of the RNAPII elongation complex, in SHM, CSR, and AID targeting.
• To elucidate the mechanism by which ELOF1 influences RNAPII transcription and its interaction with AID.

Main Methods:

• Conducted a loss-of-function genetic screen to identify SHM-related factors.
• Utilized molecular biology techniques to assess the impact of ELOF1 loss on SHM, CSR, and AID targeting.
• Analyzed RNAPII transcription dynamics, including pausing and phosphorylation states (Serine 5 and Serine 2), in the absence of ELOF1.

Main Results:

• Identified ELOF1 as a critical factor in SHM and CSR.
• Loss of ELOF1 significantly impaired SHM, CSR, and AID targeting.
• ELOF1 depletion altered RNAPII transcription by reducing pausing downstream of transcription start sites and affecting RNAPII phosphorylation at Serine 5.

Conclusions:

• ELOF1 is essential for the proper functioning of SHM and CSR.
• ELOF1 interacts with RNAPII, acting as a proximity partner for AID.
• ELOF1 likely facilitates SHM and CSR by creating a specific stalled RNAPII-transcription-coupled DNA substrate for AID action.