The Drosophila bric A brac protein and the transcriptional regulators encoded by tramt and BroadComplex contain a highly conserved domain of =115 amino acids, which we have cafled the BTB domain. We have identifed six additonal Drosophila genes that encode this domain. Five of these genes are developmentally regulated, and one of them appears to be functionally related to bric a brac. The BTB domain defines a gene family with an estimated 40 members in Drosophila. This domain is found primarily at the N terminus of zinc finger proteins and is evolutionarily conserved from Drosophia to mammals.
The amino acid sequence of human placental aromatase was determined in part (about 40%) by microsequencing methods. Using a region of overlapping peptide sequences, synthetic oligonucleotide probes were constructed and used to screen a human placental lambda gt-11 cDNA library. Of a number of positive clones, one containing a 2.4-kb insert was characterized further by restriction mapping and determination of its nucleotide sequence. The cDNA-deduced amino acid sequence is in perfect agreement with the peptide sequence data, confirming that the clone encodes for aromatase. The sequence contains a 3' untranslated region of 1.2 kb, and an open-reading frame of 1.25 kb; approximately 0.3 kb is missing from the 5' end of the coding region. While exhibiting no more than 20-30% sequence homology with other mammalian cytochromes P450, it contains the highly conserved heme-binding domain, thus confirming the essential structural requirements for this class of protein. Two cDNA fragments containing sequences coding for the amino- and carboxy-portions of the protein were used to probe for the human aromatase gene by Southern blotting. The results of these studies suggest the existence of at least two human aromatase genes. The gene encoding the aromatase cDNA we cloned was assigned to human chromosome 15 using somatic cell hybrids. This gene was mapped to band 15q21.1 by in situ hybridization studies.
The gene bric à brac (bab) is required for the proper development of the limbs and ovary in Drosophila melanogaster. bab encodes a BTB domain (also called a POZ domain), an ϳ115-amino-acid conserved motif found primarily in the N termini of zinc finger proteins. In this paper, we show that the BTB domain of bab can mediate protein dimerization in vitro. In addition, we demonstrate that the first 51 amino acids of the bab BTB domain are sufficient for dimerization, and we identify amino acids within this region that are required for binding.The gene bric à brac (bab) is required for the proper development of the limbs and ovary in Drosophila melanogaster (13,14,28). bab, which encodes a nuclear protein, has a homeotic mutant phenotype in the leg and is expressed in a discontinuous gradient along the proximal-distal axis of the tarsus. bab is also expressed in and required for the development of the terminal filaments in the larval ovary. Because terminal filaments are required for ovariole development, mutations in bab result in disorganized ovaries and female sterility.bab encodes a BTB domain, an evolutionarily conserved motif of ϳ115 amino acids found in an increasing number of proteins having a variety of functions ( Fig. 1) (13,38). The Drosophila genome contains a group of genes encoding highly conserved BTB domains, many of which have been shown to encode zinc finger domains and function as transcriptional regulators. Southern analysis suggests that there are at least 40 of these BTB domain-encoding genes in D. melanogaster (38). Other Drosophila proteins with less conserved BTB domains include kelch, a cytoplasmic protein that functions during oogenesis (34), and germ cell-less, which is found in the nuclear pores of pole cells (17,18). A number of vertebrate zinc finger proteins also contain BTB domains, including KUP (5), ZFPJS (31), ZF5 (25), ZID (2), and FBP (23). Two genes involved in human cancer also encode BTB domains: BCL-6 (35), also called LAZ3 (20), and BCL-5 (24), which is located at the sites of chromosome translocations associated with diffuse large-cell lymphoma and is thought to be the proto-oncogene specifically involved in the pathogenesis of this lymphoma. The PLZF gene is located at the sites of chromosome translocations associated with acute promyelocytic leukemia (6, 7). Several BTB domain-encoding genes in Caenorhabditis elegans and in poxviruses have been identified by genomic sequence analysis. Neither the C. elegans nor the poxvirus genes have been found to encode zinc fingers or any other known DNA binding motifs, and the functions of these genes are unknown (4,16,21,29,32,33).The BTB domain defines a family of proteins with varied activities. Understanding the function of this domain should provide a key step toward the characterization of this family. We have begun a functional analysis of the BTB domain of bab. In this paper we show that one activity of the bab BTB domain is dimerization and that this activity is restricted to the N-terminal half of the domain. This is consi...
P element transposition in Drosophila melanogaster is limited to the germ line because the third intron (the ORF2-ORF3 intron) of the P element transcript is spliced only in germ line cells. We describe a systematic search for P element sequences that are required to regulate the splicing of the ORF2-ORF3 intron. We have identified three adjacent mutations that abolish the germ line specificity and allow splicing of this intron in all tissues. These mutations define a 20-base regulatory region located in the exon, 12 to 31 bases from the 5' splice site. Our data show that this cis-acting regulatory sequence is required to inhibit the splicing of the ORF2-ORF3 intron in somatic cells.The splicing of pre-mRNA is one of the key regulatory events of gene expression in eukaryotic cells. Although much progress has been made toward understanding the biochemistry of splicing, little is known about its regulation. To further our understanding of this process, we are studying the germ line-specific splicing of the P element.P elements are transposable elements found in Drosophila melanogaster. They are the causal agents of P-M hybrid dysgenesis, a syndrome whose traits include high rates of sterility, mutation, and chromosomal rearrangement (12; for reviews see references 1, 5, and 7). P element transposition is tissue specific; transposition occurs at high rates in the germ line but is not detected in somatic tissue. Previously we have shown that the germ line specificity of P element transposition is due to germ line-specific splicing that joins open reading frame 2 (ORF2) to ORF3 (14). The first two introns of the P element are spliced in all tissues, but the ORF2-ORF3 intron is spliced only in the germ line, not in the soma (Fig. 1). cis-acting sequences must be present in the pre-mRNA which instruct the splicing machinery to splice the ORF2-ORF3 intron only in the germ line. The identification of these regulatory sequences may suggest a mechanism by which the germ line-specific splicing is regulated.Previously we have shown that a 240-base fragment that includes the third intron of the P element contains sufficient information to confer germ line specificity on the splice (15). For those experiments the ORF2-ORF3 intron of the P element was positioned between the Drosophila hsp70 (heat shock) promoter (20), plus about 1 kb of hsp70 proteincoding sequence, and the Escherichia coli lacZ gene, which encodes P-galactosidase (P-gal) (Fig. 2A). The hsp70 coding sequence was joined in frame to ORF2, and the lacZ gene was joined in frame following ORF3. For p-gal to be expressed from this construct, the hsp70 promoter must be activated and the ORF2-ORF3 intron must be spliced. The presence of P-gal activity in a heat-shocked fly containing this construct identifies tissues in which the ORF2-ORF3 intron is spliced. Because Transformants were also generated with the control construct hsp70-P(1911-[A2-3]-2183)1acZ, which differs from hsp70-P(1911-2183)-lacZ in that it contains the A2-3 deletion (a precise deletion of the ORF2...
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