RNA Processing Regulation of Immunoglobulin Gene Expression

The human genome has been found to encode a surprisingly small number of genes. However, as many as 60% of all genes may be alternatively processed to generate a much greater diversity of proteins. Thus, to fully understand gene expression, how the complex process of alternative RNA processing is regulated must be understood. This will require that well-established models for regulated processing be used to decipher the mechanistic details of these processes. The mouse immunoglobulin mu gene has been studied for many years as a model system for regulated RNA processing during B lymphocyte development. This gene contains a cleavage-polyadenylation site that is in competition with a splice reaction; the relative use of these two processing options is modulated as B cells mature to plasma cells. The arrangement and relative strengths of RNA processing signals in the Ig mu pre-mRNA is more important than gene-specific cis-acting regulatory sequences for the RNA processing regulation. This indicates that the regulation between B cells and plasma cells must involve changes in components of the general RNA processing machinery. Both cleavage-polyadenylation and splicing activity have been shown to change as B cells mature to plasma cells. In addition, other steps of RNA metabolism, including transcriptional elongation, nuclear:cytoplasmic mRNA transport and RNA stability have been shown to differ between B cells and plasma cells. The goal of this project is to identify proteins involved in regulating alternative Ig mu mRNA processing to better understand this regulatory mechanism. There is substantial evidence that the terminal differentiation program of B cells, including changes in mu-s/mu-m mRNA processing, is driven by a complex interplay of transcriptional regulators. Microarray screening will be used to identify genes whose expression changes during the developmental transition of B cells to plasma cells; some of these differentially expressed genes will encode products relevant to RNA processing regulation. Over-expression and inhibition of candidate proteins will determine their role in RNA metabolism during B cell maturation. This research will involve graduate, undergraduate, and, potentially, high school students.