Project description:The protozoan parasite Theileria parva infects and transforms bovine lymphocytes inducing uncontrolled proliferation. The transforming schizont resides free in the host cell cytoplasm and it is assumed that proteins released from the parasite contribute to host cell transformation and parasite persistence. The identification and characterisation of parasite genes encoding candidate secreted proteins constitutes a first step towards elucidating this complex process. In earlier work, it was shown that the genes encoding subtelomere-encoded variable secreted proteins (SVSPs) are located at the subtelomeres of all four T. parva chromosomes and, with 85 members, form the largest Theileria gene family. The majority of predicted proteins contain signal peptides, suggesting secretion into the host cell cytoplasm. We analysed SVSP expression in T. parva-transformed cell lines established in vitro by infection of T or B lymphocytes with cloned T. parva parasites. Preliminary microarray followed by quantitative real-time PCR analysis revealed mRNA expression for a wide range of SVSP genes. The pattern of mRNA expression was neither influenced by the cell type transformed by T. parva, nor by the animal background. Instead, the pattern of SVSP mRNA expression was largely defined by the parasite genotype and found to be relatively stable when monitored in vitro over a period of two months. Experiments using antibodies raised against the SVSP TP03_0882 provided first evidence for protein expression. Interestingly, results indicate that SVSP expression in cell lines established from a cloned parasite is limited to only a small percentage of parasites, suggesting SVSP expression by individual parasites is restricted. Expression of epitope-tagged TP03_0882 in mammalian cells revealed nuclear translocation and localisation to different nuclear compartments, including nucleoli, nucleoplasm and other nuclear bodies. Nuclear translocation to the mammalian cell nucleus was shown to involve two different types of nuclear localisation signals present in the conserved C-terminal region of TP03_0882. This first characterisation, opens up possibilities for future studies on the regulation of gene expression and the biological role of these enigmatic proteins. Expression patterns of SVSP genes in different T. parva-infected cloned cell lines Keywords: Gene expression
