Activation-Induced Cytidine Deaminase Targets DNA at Sites of RNA Polymerase II Stalling by Interaction with Spt5

SummaryActivation-induced cytidine deaminase (AID) initiates antibody gene diversification by creating U:G mismatches. However, AID is not specific for antibody genes; Off-target lesions can activate oncogenes or cause chromosome translocations. Despite its importance in these transactions little is known about how AID finds its targets. We performed an shRNA screen to identify factors required for class switch recombination (CSR) of antibody loci. We found that Spt5, a factor associated with stalled RNA polymerase II (Pol II) and single stranded DNA (ssDNA), is required for CSR. Spt5 interacts with AID, it facilitates association between AID and Pol II, and AID recruitment to its Ig and non-Ig targets. ChIP-seq experiments reveal that Spt5 colocalizes with AID and stalled Pol II. Further, Spt5 accumulation at sites of Pol II stalling is predictive of AID-induced mutation. We propose that AID is targeted to sites of Pol II stalling in part via its association with Spt5.

Graphical AbstractFigure optionsDownload high-quality image (342 K)Download as PowerPoint slideHighlights
► The Pol II stalling factor, Spt5, is required for CSR
► Spt5 interaction with AID is important for AID-Pol II association
► Spt5 colocalizes with AID at sites of Pol II stalling genome-wide in B cells
► Sites of high-density Spt5 and Pol II stalling are predictive of AID-mediated mutation