Shared and discrete interacting partners of ELL1 and ELL2 by yeast two-hybrid assay

ELL2 (eleven-nineteen lysine-rich leukemia transcription elongation factor), a component of a larger complex with pTEFb (cyclin T and CDK9) and AF4, is up-regulated in plasma cells where it influences mRNA processing by increasing exon skipping and enhancing proximal poly (A) site use. ELL2 is needed to produce the secretory-specific Ig heavy chain mRNA while ELL1 mRNA does not change in abundance with B cell stages. To investigate the potential interactions of other proteins with the ELL1 and ELL2 proteins, we preformed yeast two-hybrid studies. HSP40 and Testin were found to bind to ELL2 in its amino-terminal half. PCNA binds to ELL2 in a region encompassing amino acids 186 - 344. The potent transcription factors HIF1 α and ZNF622 interact with both ELL1 and 2 in the central, proline rich region. Meanwhile, BBS2 and ING3 interact with ELL1 but not ELL2 in this central proline-rich region. Many of the ELL-interacting-proteins uncovered in the two-hybrid screen are tumour suppressors that may work through the ELL: pTEFb complex to suppress or activate sets of genes in plasma cells.