Chicken repeat 1 (CR1) elements, which define an ancient family of vertebrate non-LTR retrotransposons, contain two closely spaced open reading frames.
Chicken repeat 1 (CR1) elements comprise a family of non-long terminal repeat (LTR) retrotransposons that have several noteworthy features. For example, whereas most other non-LTR elements have poly(A) tracts or other simple A-rich repeats at their 3' ends, the 3' ends of CR1 elements conform to the consensus [(CATTCTRT)(GATTCTRT)1-3]. CR1 elements also display an unusual bias for severe 5' truncations: only approx. 30 (out of a total of approx. 30 000) CR1 elements in the chicken genome include significant portions of the pol-like open reading frame (ORF) that we previously identified and partially sequenced [Burch et al. (1993) Proc. Natl. Acad. Sci. USA 90, 8199-8203]. In the present study we derived a consensus sequence for this entire ORF (ORF2) as well as an upstream ORF (ORF1) and part of a 5' untranslated region (UTR). The conceptual translation product of ORF2 is predicted to contain an endonuclease domain in addition to a reverse transcriptase domain. These results suggest that CR1 elements retrotranspose using a "nick and prime" mechanism similar (but not identical) to other families of non-LTR elements.
Haas
N B
NB
Institute for Cancer Research, Fox Chase Cancer Center, Philadelphia, PA 19111, USA.
Grabowski
J M
JM
Sivitz
A B
AB
Burch
J B
JB
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002645:Chickens / Q000235:genetics*; D016384:Consensus Sequence / Q000235:genetics; D004720:Endonucleases / Q000235:genetics; D008969:Molecular Sequence Data; D016366:Open Reading Frames / Q000235:genetics*; D012194:RNA-Directed DNA Polymerase / Q000235:genetics; D012091:Repetitive Sequences, Nucleic Acid / Q000235:genetics*; D018626:Retroelements / Q000235:genetics*; D012689:Sequence Homology, Nucleic Acid
D018626:Retroelements; D012194:RNA-Directed DNA Polymerase; D004720:Endonucleases