Characterization of LINE-1 ribonucleoprotein particles.

The average human genome contains a small cohort of active L1 retrotransposons that encode two proteins (ORF1p and ORF2p) required for their mobility (i.e., retrotransposition).

piRNA-mediated nuclear accumulation of retrotransposon transcripts in the Drosophila female germline.

Germline silencing of transposable elements is essential for the maintenance of genome integrity. Recent results indicate that this repression is largely achieved through a RNA silencing pathway that involves Piwi-interacting RNAs (piRNAs). However the repressive mechanisms are not well understood.

Distinct mechanisms for trans-mediated mobilization of cellular RNAs by the LINE-1 reverse transcriptase.

Long Interspersed Element-1 (LINE-1 or L1) sequences comprise approximately 17% of human DNA and ongoing L1 retrotransposition continues to impact genome evolution. The L1-encoded proteins also can mobilize other cellular RNAs (e.g.

The flamenco locus controls the gypsy and ZAM retroviruses and is required for Drosophila oogenesis.

In Drosophila, the as yet uncloned heterochromatic locus flamenco (flam) controls mobilization of the endogenous retrovirus gypsy through the repeat-associated small interfering (rasi) RNA silencing pathway. Restrictive alleles (flamR) downregulate accumulation of gypsy transcripts in the somatic follicular epithelium of the ovary. In contrast, permissive alleles (flamP) are unable to repress gypsy.

A novel repeat-associated small interfering RNA-mediated silencing pathway downregulates complementary sense gypsy transcripts in somatic cells of the Drosophila ovary.

Replication of the gypsy endogenous retrovirus involves contamination of the female germ line by adjacent somatic tissues. This is prevented by flam, an as-yet-uncloned heterochromatic pericentromeric locus, at the level of transcript accumulation in these somatic ovarian tissues. We tested the effect of a presumptive RNA silencing mechanism on the accumulation of RNAs produced by constructs containing various gypsy sequences and report that the efficiency of silencing is indeed correlated with the amount of complementary RNAs, 25 to 30 nucleotides in length, in the ovary.