Gene Arrays at Pneumocystis carinii Telomeres

In the fungus Pneumocystis carinii, at least three gene families (PRT1, MSR, and MSG) have the potential to generate high-frequency antigenic variation, which is likely to be a strategy by which this parasitic fungus is able to prolong its survival in the rat lung. Members of these gene families are...

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Published in:	Genetics (Austin) 2005-08, Vol.170 (4), p.1589-1600
Main Authors:	Keely, Scott P, Renauld, Hubert, Wakefield, Ann E, Cushion, Melanie T, Smulian, A. George, Fosker, Nigel, Fraser, Audrey, Harris, David, Murphy, Lee, Price, Claire, Quail, Michael A, Seeger, Kathy, Sharp, Sarah, Tindal, Carolyn J, Warren, Tim, Zuiderwijk, Eduard, Barrell, Barclay G, Stringer, James R, Hall, Neil
Format:	Article
Language:	eng
Subjects:	Amino Acid Sequence Antigens, Fungal Base Sequence Chromosome Mapping Chromosomes, Fungal Cloning, Molecular Cosmids DNA, Fungal Evolution, Molecular Gene Duplication Gene Expression Regulation, Fungal Gene Library Genes Genes, Fungal Genetic Linkage Genetics Genome, Fungal Investigations Open Reading Frames Pneumocystis carinii Pneumocystis carinii - genetics Pneumonia Population Proteins Recombination, Genetic Repetitive Sequences, Nucleic Acid RNA, Messenger - genetics Selection, Genetic Sequence Analysis, DNA Sequence Homology, Nucleic Acid Telomere - genetics
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Summary:	In the fungus Pneumocystis carinii, at least three gene families (PRT1, MSR, and MSG) have the potential to generate high-frequency antigenic variation, which is likely to be a strategy by which this parasitic fungus is able to prolong its survival in the rat lung. Members of these gene families are clustered at chromosome termini, a location that fosters recombination, which has been implicated in selective expression of MSG genes. To gain insight into the architecture, evolution, and regulation of these gene clusters, six telomeric segments of the genome were sequenced. Each of the segments began with one or more unique genes, after which were members of different gene families, arranged in a head-to-tail array. The three-gene repeat PRT1-MSR-MSG was common, suggesting that duplications of these repeats have contributed to expansion of all three families. However, members of a gene family in an array were no more similar to one another than to members in other arrays, indicating rapid divergence after duplication. The intergenic spacers were more conserved than the genes and contained sequence motifs also present in subtelomeres, which in other species have been implicated in gene expression and recombination. Long mononucleotide tracts were present in some MSR genes. These unstable sequences can be expected to suffer frequent frameshift mutations, providing P. carinii with another mechanism to generate antigen variation.
ISSN:	0016-6731 1943-2631 1943-2631