We have been continuing our analysis of
ama-1 IV and envirous, the cloning of which has been reported in a previous edition (WBG, 9(1)). Using a conventional walking approach, we have expanded the area around the region of Drosophila homology to about 29 kb [Sulston and Coulson et al. were unable to find a cosmid contig, perhaps as a result of the paucity of HindIII sites]. About 20 kb of the
ama-1 region is shown in Figure 1. Using restriction fragments spanning this region (bottom line of Figure I ), we have, barring any very large introns, delineated the approximate extent of the region encoding the 5.9 kb
ama-1 transcript. Based on hybridization signal strength,
ama-1 transcripts are about 150 times less abundant than
unc-54 transcripts in total RNA. While doing northerns, we observed that a probe approximately 5 kb rightward of ama- I detected an abundant smear of transcripts at 1.2 - 1.4 kb. Since this resembled the pattern for a collagen probe, we sent a flanking sequence to Jim Kramer who very kindly screened the collagen gene bank (Cox et al., MCB, 4, 2389, 1984), identifying this as the collagen gene in CG41. CG41 extends an additional 2 kb more rightward than shown in Figure 1. This collagen gene has been assigned the gene name
col-33.{Figure 1} The analogues of ama- I in yeast (RP02 1 ) and mouse have been sequenced (Allison et aL, Cell, 42, 599, 1985; M. Bartolemei, personal communication). Both were found to encode a C-terminal domain comprised of an heptapeptide, with consensus [tyr-ser-pro-thr-ser-pro- ser], tandemly repeated (26 times in yeast and 52 times in mouse). Loss of this domain during preparation of the pol II enzyme from yeast cells results in a characteristic 190 k degradation product, which is also observed for C. M. Golomb, personal communication), suggesting that worms may also have this strange tail.