The sequence of a large L1Md element reveals a tandemly repeated 5' end and several features found in retrotransposons.

Abstract

The complete nucleotide sequence of a 6,851-base pair (bp) member of the L1Md repetitive family from a selected random isolate of the BALB/c mouse genome is reported here. Five kilobases of the element contains two overlapping reading frames of 1,137 and 3,900 bp. The entire 3,900-bp frame and the 3' 600 bp of the 1,137-bp frame, when compared with a composite consensus primate L1 sequence, show a ratio of replacement to silent site differences characteristic of protein coding sequences. This more closely defines the protein coding capacity of this repetitive family, which was previously shown to possess a large open reading frame of undetermined extent. The relative organization of the 1,137- and 3,900-bp reading frames, which overlap by 14 bp, bears resemblance to protein-coding, mobile genetic elements. Homology can be found between the amino acid sequence of the 3,900-bp frame and selected domains of several reverse transcriptases. The 5' ends of the two L1Md elements described in this report have multiple copies, 4 2/3 copies and 1 2/3 copy, of a 208-bp direct tandem repeat. The sequence of this 208-bp element differs from the sequence of a previously defined 5' end for an L1Md element, indicating that there are at least two different 5' end motifs for L1Md.

Unusual expression of LINE-1 transposable element in the MRL autoimmune lymphoproliferative syndrome-prone strain

“…Similar to Northern-blot analyses, these studies indicated fewer antisense transcripts ( (Loeb et al, 1986) of the probes Cellular localization of LINE-1 ORF2 transcripts LINE-1 sense-strand transcripts were detected by ISH in spleen, LN, thymus and liver of MRL/lpr, MRL-+/+ and LG strains ( Figure 2B and data not shown). In the MRL-+/+ and LG strains, LINE-1 sense transcripts were mainly localized in splenic germinal centres ( Figure 2B,a,b), LN cortex, which contains germinal centres ( Figure 2B,c,d), and thymic cortex, which contains proliferating immature T-cells ( Figure 2B,e,f).…”

“…Some transcripts were 57 kb in length; the 7-kb transcripts may represent full-length LINE-1 transcripts endowed with transcriptional regulatory activity with A-and F-type monomers at their 5' end (Loeb et al, 1986;Padgett et al, 1988;Severynse et al, 1992). Indeed, using 5' monomer probes from a LINE-1 region endowed with promoter activity, we observed full-length transcripts in various organs (unpublished results).…”

“…Probes LINE-1 strand-specific RNA probes (Figure 1, bottom) were obtained after in vitro transcription of the 13A3a cDNA (Bobe´et al, 1993) homologous to nucleotides 5273 to 6109 of the LINE-1 L1Md-A2 clone (Loeb et al, 1986) subcloned into the Bluescribe pBS plasmid vector (Stratagene, La Jolla, CA, USA). This plasmid was then linearized and transcribed using T3 or T7 RNA polymerase (Stratagene) to obtain RNA probes complementary to the LINE-1 sense or antisense strands, respectively (arrows in Figure 1).…”

Molecular population studies of Simulium damnosum s.l. (Diptera: Simuliidae) using a novel interspersed repetitive DNA marker

“…Among several similarities found was a match to the C terminal end of an Li retrotransposon protein sequence from Mus domestica (Loeb et al, 1986).…”

Mutation and psychosis: a suggested explanation of seasonality of birth

“…A recent paradigm is the the LINE LIMd element in the mouse. This has the structure of a mobile genetic element and includes a protein coding sequence and variable 5' tandem repeat; it is suggested (Loeb et al 1986) that the length of the tandem repeat regulates transcription of the protein. The suggestion that a component of the element is variable between generations implies that the 'virogene' is located at a 'hot-spot' in the genome, i.e.…”