In vivo RNA localization of I factor, a non-LTR retrotransposon, requires a cis-acting signal in ORF2 and ORF1 protein.
According to the current model of non-LTR retrotransposon (NLR) mobilization, co-expression of the RNA transposition intermediate, and the proteins it encodes (ORF1p and ORF2p), is a requisite for the formation of cytoplasmic ribonucleoprotein complexes which contain necessary elements to complete a retrotransposition cycle later in the nucleus. To understand these early processes of NLR mobilization, here we analyzed in vivo the protein and RNA expression patterns of the I factor, a model NLR in Drosophila. We show that ORF1p and I factor RNA, specifically produced during transposition, are co-expressed and tightly co-localize with a specific pattern (Loc+) exclusively in the cytoplasm of germ cells permissive for retrotransposition. Using an ORF2 mutated I factor, we show that ORF2p plays no role in the Loc+ patterning. With deletion derivatives of an I factor we define an RNA localization signal required to display the Loc+ pattern. Finally, by complementation experiments we show that ORF1p is necessary for the efficient localization of I factor RNA. Our data suggest that ORF1p is involved in proper folding and stabilization of I factor RNA for efficient targeting, through Loc+ patterning, to the nuclear neighborhood where downstream steps of the retrotransposition process occur.
Seleme
Maria del Carmen
MC
Institut de Génétique Humaine, C.N.R.S. 141 rue de la Cardonille, 34396 Montpellier, France.
Disson
Olivier
O
Robin
Stéphanie
S
Brun
Christine
C
Teninges
Danielle
D
Bucheton
Alain
A
D000818:Animals; D001483:Base Sequence; D004330:Drosophila / Q000235:genetics*; D029721:Drosophila Proteins / Q000032:analysis / Q000235:genetics* / Q000502:physiology*; D005260:Female; D009154:Mutation; D009865:Oocytes / Q000737:chemistry; D009866:Oogenesis / Q000235:genetics; D010641:Phenotype; D012333:RNA, Messenger / Q000032:analysis* / Q000737:chemistry; D012194:RNA-Directed DNA Polymerase / Q000235:genetics* / Q000502:physiology; D038621:Regulatory Sequences, Ribonucleic Acid; D018626:Retroelements; D017384:Sequence Deletion
D029721:Drosophila Proteins; C117553:I-element-gag protein, Drosophila; C496854:ORF2 protein, Drosophila; D012333:RNA, Messenger; D038621:Regulatory Sequences, Ribonucleic Acid; D018626:Retroelements; D012194:RNA-Directed DNA Polymerase