A novel tripartite structure comprising a mariner-like element and two additional retrotransposons found in the Bombyx mori genome.
A clone of a DNA-mediated mobile element (transposon) corresponding to a mariner-like element (MLE) was obtained by carrying out the polymerase chain reaction with genomic DNA of Bombyx mori using a Hyalophora cecropia MLE sequence as a primer. This clone had a size of about 4.2 kb and, after sequencing, was found to contain an RNA-mediated, shorter retrotransposon named L1Bm, which was in turn integrated with a much longer retrotransposon named BMC1. Thus, the mobile elements made a novel tripartite structure. The BMC1 and L1Bm moieties of the composite structure each contained a 63-bp conserved sequence which was subsequently found to be highly conserved in all BMC1 and L1Bm elements registered so far. We propose that the 63-bp stretch may be a recognition site for a retrotransposition mechanism conducted by a reverse transcriptase and an endonuclease complex. On the basis of this inference, we propose a model that predicts how different types of BMC1 and L1Bm elements are dispersed in the genome. In addition, a phylogenetic tree made from the current and extant BMC1 and L1Bm sequences indicated that these elements can be classified into Subfamilies I and II.
Nakajima
Y
Y
Gene Research Center, University of the Ryukyus, Chihara 1, Nishihara-cho, Okinawa 903-0213, Japan.
Hashido
K
K
Tsuchida
K
K
Takada
N
N
Shiino
T
T
Maekawa
H
H
D000818:Animals; D001483:Base Sequence; D012831:Bombyx / Q000235:genetics*; D003001:Cloning, Molecular; D017124:Conserved Sequence; D004247:DNA / Q000235:genetics; D017931:DNA Primers / Q000235:genetics; D019143:Evolution, Molecular; D017344:Genes, Insect; D016678:Genome; D008957:Models, Genetic; D008969:Molecular Sequence Data; D010802:Phylogeny; D018626:Retroelements / Q000235:genetics*; D012689:Sequence Homology, Nucleic Acid
D017931:DNA Primers; D018626:Retroelements; D004247:DNA