The engrailed locus of Drosophila: structural analysis of an embryonic transcript

cDNA clones originating from the engrailed gene of Drosophila have been isolated from recombinant phage libraries that were made using poly(A)+ RNA extracted from early embryos. The DNA sequence of one of these clones includes a homeo box, a 180 bp sequence present in several other Drosophila genes important in formation of body pattern during development. The homeo boxes found in the other Drosophila genes, as well as in cognate sequences from a wide range of segmented animals, including higher vertebrates, are highly conserved. By contrast, the homeo box within the engrailed gene diverges substantially and, unlike the other homeo boxes, is interrupted by an intervening sequence. The engrailed homeo box is located near the 3' end of a 1700 bp open reading frame. If translated, this sequence would produce a protein of unusual composition. We also show that a neighboring gene has a large region with strong homology to engrailed, and that it also contains a homeo box.     

Sequence analysis of the murine Hox-2.2, -2.3, and -2.4 homeo boxes: evolutionary and structural comparisons

We have determined the nucleotide sequences and deduced the amino acid sequences of three tandemly arranged murine boxes of the Hox-2 homeo box gene complex on mouse chromosome 11 (Hox-2.2, -2.3, and -2.4). The type and position of differences with other sequenced homeo boxes were analyzed. Hox-2.2 is nearly identical with its cognate human homeo box Hu-2. Hox-2.3 shares 59 of 61 amino acids with the Antennapedia homeo domain of Drosophila and the MM-3 homeo domain of Xenopus and shows 60 of 61 amino acid identity with human HuC1. Hox-2.3, MM-3, and HuC1 also share a stretch of six glutamic acid residues followed by a stop codon 15-20 amino acids 3' of the homeo domain. Hox-2.4 is relatively divergent from most of the other homeo boxes sequenced to date; however, it matches the Hox-3.1 murine homeo domain at 60 of 61 positions. Sequence comparisons with other murine homeo domains, together with previous studies of their genomic organization and chromosomal location, provide support for the hypothesis of a large-scale duplication resulting in the two major murine homeo box gene complexes Hox-1 and Hox-2.     

The murine Hox-2 cluster of homeo box containing genes maps distal on chromosome 11 near the tail-short (Ts) locus

Two probes derived from a mouse recombinant lambda-clone (H24.1), that contains a sequence closely homologous to the Drosophila antennapedia homeo box, were mapped to mouse chromosome (MMU) 11 by filter hybridization of somatic cell hybrid DNA. This sequence is highly homologous to a human homeo box gene (HOX2) and appears to represent one of the two genes in the Hox-2 cluster previously assigned to MMU 11. To regionally map the Hox-2 cluster, we have carried out in situ hybridization of the two H24.1 probes and of an independently isolated Hox-2 probe. The autoradiographic silver grain distributions were similar in all three experiments with a peak over band 11D. This region contains the locus for the tail-short (Ts) mutation which causes skeletal abnormalities in heterozygotes and early embryonic death in homozygotes.     

The YYRR box: a conserved dipyrimidine-dipurine sequence element in Drosophila and other eukaryotes.

We have discovered a novel DNA sequence element in Drosophila which is based upon a CTGA tandem repeat. This element has been named the YYRR box to emphasize its dipyrimidine-dipurine nature which is predicted to have unusual structural features. Southern hybridization analysis of genomic DNA indicates the presence of 25-30 copies of the YYRR box in each of three Drosophila species (melanogaster, pseudoobscura, and virilis) and conservation of genomic location within species. Similar analysis of human and rat DNA indicates the presence of YYRR related sequences in mammals as well. YYRR boxes have been localized to two genetic loci in Drosophila: Gld and a gene tentative identified as ted. These two genes exhibit correlated patterns of developmental expression and an identical mutant phenotype. Sequence analysis of the Gld YYRR box in three Drosophila species revealed a high degree of conservation despite its intronic location.     

Characterization of five members of the actin gene family in the sea urchin

Hybridization of an actin cDNA clone (pSA38) to restriction enzyme digests of Strongylocentrotus purpuratus DNA indicates that the sea urchin genome contains at least five different actin genes. A sea urchin genomic clone library was screened for recombinants which hydridize to pSA38 and four genomic clones were isolated. Restriction maps were generated which indicate that three of these recombinants contain different actin genes, and that the fourth may be an allele to one of these. The restriction maps suggest that one clone contains two linked actin genes. This fact, which was confirmed by heteroduplex analysis, indicates that the actin gene family may be clustered. The linked genes are oriented in the same direction and spaced about 8.0 kilobases apart. In heteroduplexes between genomic clones two intervening sequences were seen. Significant homology is confined to the actin coding region and does not include any flanking sequence. Southern blot analysis reveals that repetitive DNA sequences are found in the region of the actin genes.     

Isolation and characterization of a sea urchin hsp 70 gene segment

Three clones containing Paracentrotus lividus sea urchin DNA sequences which cross-hybridize to Drosophila heat shock protein (hsp) 70 gene were isolated. The sequence arrangements in the three cloned DNA inserts were compared by restriction and cross-hybridization analysis. The results showed that they contain four different genes related to one Drosophila hsp 70 gene. One of these genes was subcloned, and two of the isolated fragments were shown to hybridize to genomic DNA and to RNA from heat-treated sea urchin embryo.