Cloning and characterization of a transposable-like repeat in the heterochromatin of the darkling beetle Misolampus goudoti.
A long repeat unit of the PstI family in Misolampus goudoti (Coleoptera, Tenebrionodae) is characterized in this work. The 30 sequenced units have small differences in length (consensus 1169 bp), but very similar nucleotide composition (mean 61.1% A+T). PstI repeats contain a 36-bp-long inverted repeat at both the 5' and 3' ends, with a fully conserved 16-bp-long motif similar to those found in class II transposable elements. However, the transposable-like PstI repeats seems to be defective, since they do not encode for any protein related with transposition. Interestingly, energetically stable hairpins resembled the structure of a miniature interspersed transposable element, suggesting that the PstI satellite DNA family in M. goudoti may have originated from an ancestral active transposable element as also described in Drosophila guanche. The presence of transposable-like structure along with the non-detection of gene conversion or unequal crossing-over events suggest that transposition could be one of the putative molecular mechanisms involved in the strong amplification and (or) homogenization of these repeats. A putative transposition of PstI repeats allowing their genomic mobility also could explain why this satellite is widely distributed to all heterochromatic regions, telomeres, pericentromeric regions, and on the Y chromosome, whereas satellites of other tenebrionids lacking transposable-like structures are restricted only to pericentromeric regions.
Pons
Joan
J
Department of Entomology, The Natural History Museum, Cromwell Road, London SW7 5BD, USA. joap@nhm.ac.uk
D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D001517:Coleoptera / Q000235:genetics*; D016384:Consensus Sequence; D004247:DNA / Q000737:chemistry / Q000235:genetics; D004251:DNA Transposable Elements / Q000235:genetics*; D015252:Deoxyribonucleases, Type II Site-Specific; D019143:Evolution, Molecular; D006570:Heterochromatin / Q000235:genetics; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation
D004251:DNA Transposable Elements; D006570:Heterochromatin; D004247:DNA; C024388:CTGCAG-specific type II deoxyribonucleases; D015252:Deoxyribonucleases, Type II Site-Specific