Repeated long final sequence

A repeated long final sequence (in English Long Terminal Repeat sequence or LTR) is a sequence nucleotidic present and integrated in DNA of the cells eucaryotes, and which in addition constitute often ends 5 ' and 3 ' of the Rétrotransposon S.

LTR of the Ty elements

Name and size

The genome of the yeast Saccharomyces cerevisiae contains five families of rétrotransposons: Ty1 with Ty5. The LTR of these 5 elements are different in the face and sequence and are indicated by Greek letters.

Composition

They all are subdivided in three areas, indicated compared to their position on the ARNm: U3 (for single in 3' of ARN), R (for repeated at the two ends of the ARN) and U5 (for single in 5' of the ARN).

Studies undertaken on the effect of délétions of fragments or substitutions of bases of the sequence of the solo-LTR his4-912δ showed that in fact the LTR have all the signals necessary for the starting and the termination of the transcription by the ARN polymerase II (Fulton and Al 1988; Hirschman and Al 1988; Dudley and Al 1999). The sequences promotrices (box TOUCHED) are active only on the level of the LTR into 5', because they require the presence of regulating areas of the transcription, downstream localized in the beginning of coding phase TYA (Fulton and Al 1988). On the other hand, the sites of polyadenylation are active only on the level of the LTR into 3', because they require the presence of regulating areas present only in part 3' of ARNm Ty (Hou and Al 1994). The area R of the LTR is found at the two ends of transcribed and is essential for the opposite transcription of this ARNm in ADNc.

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