LTR retrotransposon

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Under LTR retrotransposons is understood transposable (moving) items in the genome , which as an intermediate RNA use ( retroelements ) and long terminal repeats are flanked (LTR). The LTRs are 250–600 bp long and aligned in the same direction ( direct repeats ). In addition, there are also inverted repeats , which play an important role in retrotransposition, but are much smaller.

construction

LTR retrotransposons typically contain a gag ( group-specific antigen ) and a pol gene. The pol gene codes for a protein that has activity for a reverse transcriptase , for an RNase H, for a protease and an integrase.

Various representatives, such as the gypsy family, also have a defective gene for an envelope protein ( env for envelop ). Thus, LTR retrotransposons consist of the same elements as retroviruses , with the envelope proteins either defective or deleted, so that they can be regarded as very close relatives of the retroviruses.

Important representatives

Important families are the TY1-copia family in all green plants ( algae to higher plants) and the TY3-gypsy family in seed plants . LTR retrotransposons can also be found in animals.
In the human genome , they make up around 8.5%. The largest family, the HERVs ( human endogenous retro virus ) make up about 4.7%, the MaLR ( mammalian apparent LTR-retrotransposon ) make up about 3.8%.

meaning

For the meaning, see also the section in the article: LTR element .

literature

  • JD Boeke, VD Corces: Transcription and reverse transcription of retrotransposons In: Annu. Rev. Microbiol. 43, 1989, pp. 403-34.