Attachment of HeT-A sequences to chromosomal termini in Drosophila melanogaster may occur by different mechanisms.
Drosophila telomeres contain arrays of the retrotransposonlike elements HeT-A and TART. Their transposition to broken chromosomal termini has been implicated in chromosome healing and telomere elongation. The HeT-A element is attached by its 3' end, which contains the promoter. To monitor the behavior of HeT-A elements, we used the yellow gene with terminal deficiencies consisting of breaks in the yellow promoter region that result in the y-null phenotype. Attachment of the HeT-A element provides the promoterless yellow gene with a promoter that activates yellow expression in bristles. The frequency of HeT-A transpositions to the yellow terminal deficiency depends on the genotype of the line and varies from 2 x 10(-3) to less than 2 x 10(-5). Loss of the attached HeT-A due to incomplete replication at the telomere leads to inactivation of yellow expression, which is restored by attachment of a new HeT-A element upstream of yellow. New HeT-A additions occur at a frequency of about 1.2 x 10(-3). Short DNA attachments are generated by gene conversion using the homologous telomeric sequences as templates. Longer DNA attachments are generated either by conventional transposition of an HeT-A element to the chromosomal terminus or by recombination between the 3' terminus of telomeric HeT-A elements and the receding end of HeT-A attached to the yellow gene.
Kahn
T
T
Department of Control of Genetic Processes, Institute of Gene Biology, Russian Academy of Sciences, 117334 Moscow, Russia.
Savitsky
M
M
Georgiev
P
P
D000818:Animals; D001483:Base Sequence; D004247:DNA / Q000096:biosynthesis* / Q000235:genetics; D004261:DNA Replication / Q000235:genetics; D029721:Drosophila Proteins; D004331:Drosophila melanogaster / Q000235:genetics*; D005785:Gene Conversion / Q000235:genetics; D015870:Gene Expression; D005838:Genotype; D019476:Insect Proteins / Q000235:genetics; D008969:Molecular Sequence Data; D010641:Phenotype; D011401:Promoter Regions, Genetic / Q000235:genetics; D015183:Restriction Mapping; D018626:Retroelements / Q000235:genetics*; D017384:Sequence Deletion; D012689:Sequence Homology, Nucleic Acid; D016615:Telomere / Q000235:genetics* / Q000378:metabolism; D015533:Transcriptional Activation
D029721:Drosophila Proteins; D019476:Insect Proteins; D018626:Retroelements; C050680:y protein, Drosophila; D004247:DNA