The central MHC gene, BAT1, may encode a protein that down-regulates cytokine production

Background: BAT1 belongs to the DEAD-box family of RNA-binding proteins and is encoded in the central MHC. To determine whether it affects immune responses and hence diseases influenced by MHC haplotypes, U937, THP1 and Jurkat cells were stably transfected with anti-sense DNA corresponding to exons 2-5 of BAT1 using a retroviral vector. Results: Anti-sense transfectants carried anti-sense DNA and expressed anti-sense mRNA. After mitogenic stimulation, they produced higher levels of TNF alpha, IL-1 and IL-6 than equivalent cells carrying the vector alone, suggesting that BAT1 may downregulate acute phase cytokine production. Polyclonal antibodies raised against a peptide in exon 8 of BAT1 recognized approximate to 50 kDa and approximate to 38 kDa proteins in all cell lines tested, including the anti-sense transfectants. Expression was localized to the nucleolus in dividing fibroblasts. However the immunochemistry may be confounded by a recently described gene, DDXL, on chromosome 19, which shares a 89% amino acid identity with BAT1. RT-PCR analyses established that BAT1 and DDXL mRNA are expressed in resting U937, THP1 and Jurkat cells. BAT1 and DDXL are divergent in the exons selected for the anti-sense study. Conclusions: BAT1 is a negative regulator of inflammation. Future studies should address how its functions relate to those of DDXL.