Our lab has generated 142 essential gene mutations defining 112 genes under sDp3 , on chromosome III. We have divided the region between
dpy-17 and
dpy-19 into 12 zones that are defined by overlapping deficiencies and duplications. These zones were determined physically by PCR testing the deficiencies to determine endpoints. We have mapped the 112 essential gene mutations into these zones. One such region is deleted by sDf125 . This region spans 420 000 base pairs and is completely covered by sequenced cosmids. Within this zone there are 107 predicted coding elements, many of which with similarities to mitochondrial and ribosomal-associated proteins. To date, we have mapped 17 essential genes into this zone. Using transgenics from our lab's cosmid transgenic library, we positioned 13 of the 17 genes to cosmids. 12 of the 13 genes lie in the rightmost 250 kB of the region. This distribution could be due to the large number of olfactory receptors in the left half of this region. We have begun subcloning the rescued genes in this essential gene rich region and have positioned several of them to single predicted coding elements.
let-716 encodes the worm orthologue of RRP5 (C16A3.3). RRP5 is an essential rRNA biogenesis protein in yeast. It is required for the processing of at least three of the four ribosomal RNA molecules (18S, 5.8S and 28S). This processing occurs in the nucleolus of the yeast cell. Both alleles of
let-716 block as L1 larvae. As mentioned above, this region is rich in ribosome-associated proteins and we are looking at other lethal mutations which may be part of ribosomal biogenesis.
let-721 encodes electron transfer flavoprotein-ubiquinone oxidoreductase (C05D11.12). This protein is essential for proper mitochondrial electron transfer. C05D11.12 encodes one of many electron transport proteins found in this region. Two NADH ubiquinone oxidoreductases (C16A3.4 & T26A5.3) are also in this region. We have two alleles of
let-721 , one arrests as a sterile adult while the other is a maternal effect lethal. The Mel allele is male rescueable. We have made a LET-721:GFP fusion protein and are currently looking at its localization.