PAM1, an RNA Binding Protein Required for Chromosome Dynamics in Meiosis

During prophase I of meiosis, chromosomes engage in complex interactions and exhibit very dynamic behavior, which are essential for their proper pairing, recombination, and later, segregation to daughter cells. A hallmark of this process is the formation of the telomere bouquet, which consists of telomeres of all chromosomes clustering on the nuclear envelope. These activities are part of a general reorganization of the nucleus, which also involves clustering of nuclear pores. In maize, many of these processes are controlled by the Pam1 (plural abnormalities of meiosis 1) gene. Pam1 is required for the bouquet formation and proper chromosome pairing. pam1 mutants also show significantly decreased chromosome motility in early meiotic prophase, which is likely caused by a cytoskeleton defect. Clustering of nuclear pores is also abnormal. We cloned the Pam1 gene and found that encodes an RNA-binding protein. We discovered that the gene controls transcript levels of a fairy small subset of genes expressed during meiosis. Pam1 also affects transcript splicing. We performed RNA immunoprecipitation experiments using PAM1-specific antibodies and found that the protein binds roughly 150 mRNA species. Most of these mRNAs represent genes encoding proteins involved in RNA processing, protein synthesis, and degradation. Overall, our data suggest that Pam1 affects nuclear dynamics by controlling a gene regulation network that is responsible for a subset of cellular processes taking place during the prophase of meiosis