Mobile dispersed genetic element MDGI of Drosophila melanogaster: transcription pattern

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Abstract
Virtually the whole region of the mobile dispersed genetic element mdg1 including the direct repeats that frame mdg1 /1/ is transcribed. The end of the transcriptional unit is located within the direct repeat. Although the transcription of mdg1 is symmetric, one direction is transcribed preferentially and is a full-length transcript represented by˜ 2 poly(A)+RNA. Besides it,˜15S poly(A)+RNA is present in the cytoplasm of culture cells which corresponds to the 3′-part of 29S RNA and possibly to a small region near the 5′-end of the latter. The major fraction of mdg1 transcripts is present in the fraction of free cytoplasmic RNP particles while only 10–20% are recovered in polysomes. In this respect, mdg1 is similar to mdg3 and quite different from two single-copy genes transcripts of which are almost completely recovered in polysomes. The relationship between mobile dispersed genetic elements and endogeneous viral genomes is discussed.