Precise limitation of concerted evolution to ORFs in mosquito Hsp82 genes

Abstract

Two Hsp82 genes were isolated from the malaria vector Anopheles albimanus in a single lambda phage clone. The two genes are in a head-to-head arrangement separated by approx. 0.9 kbp. Northern hybridizations and 5' RACE demonstrate that both genes are transcribed, have moderate levels of constitutive transcription, and are also heat-inducible with maximum transcript accumulation occurring after 40 degrees C heat shocks. Both genes have typical heat-shock promoters and conserved intron boundaries in the untranslated leaders. The open reading frames are 99.6% identical differing in only nine silent nucleotide positions in the 2166 bp ORFs. However, precisely outside the ORFs, the flanking DNA of the two genes shows no evidence of common derivation. The high degree of identity between the two ORFs appears to be a result of gene conversion occurring by a process similar to that previously suspected in the A. albimanus Hsp70 genes and several D. melanogaster genes arranged as palindromes. This process probably involves a stem-loop intermediate and is restricted in extent by flanking sequence divergence. These Hsp82 genes clearly demonstrate the extreme precision with which gene conversion can lead to protein-coding-region homogeneity yet allow flanking DNA divergence.

Extensive gene amplification and concerted evolution within the CPR family of cuticular proteins in mosquitoes

“…In contrast to this model, RR-2 sequence clusters are not characterized by an erosion of sequence similarity within the coding sequence, but generally experience rapid decline in flanking nucleotide sequence ( Fig. 7 and Supplementary File 7; an even more striking case was found for Anopheles albimanus heat shock proteins by Benedict et al (1996)). We also do not observe an escape from gene conversion caused by the accumulation of barriers to non-orthologous recombination within large tandem arrays of CPR genes.…”

Isolation and characterization of two cytoplasmic hsp90s from Mytilus galloprovincialis (Mollusca: Bivalvia) that contain a complex promoter with a p53 binding site

“…In vertebrates, there are two cytoplasmic isoforms, namely the α (heat-inducible) and the β (constitutively expressed or cognate) (Krone and Sass, 1994;Gupta, 1995;Chen et al, 2006). In invertebrates, a unique cytoplasmic Hsp90 is encoded either by a single or by two gene copies (Blackman and Meselson 1986;Benedict et al, 1996;Birnby et al, 2000;Chen et al, 2006). An inducible and a cognate isoform exist in Saccharomyces cerevisiae (Gupta, 1995;Erkine et al, 1995Erkine et al, , 1999, whereas multiple identical copies code for the same Hsp90 in protists (Mottram et al, 1989).…”

Molecular cloning, characterization and expression of heat shock protein 90 gene in the haemocytes of bay scallop Argopecten irradians

“…HSP90b lacked the glutamine-rich sequence (QTQDQ) at the N-terminus compared with HSP90a [36]. Until now, only one type HSP90 has been reported in invertebrates except Anopheles albimanus which contains two HSP90 genes [37]. To our knowledge, most studies of HSP90 are focused on mammals and typical model organisms, while the molecular features and functional studies in mollusk remain deficient and only HSP90s from Chlamys farreri and Haliotis tuberculata have been cloned and characterized [38,39].…”