ABSTRACTS:

TITLE: CHARACTERIZATION OF THE TWO H1(ZERO)CODING GENES FROM XENOPUS LAEVIS.
AUTHOR: BROCARD MP, TRIEBE S, PERETTI M, DOENECKE D, HOCHBIN S
JOURNAL: GENE 1997 Apr 11; 189(1):127-34
ABSTRACT: We have analyzed the promoter and the coding sequences of the two homologous histone H1(zero)-encoding genes from Xenopus laevis, here termed H1(zero)-1 and H1(zero)-2. Both genes encode proteins of 193 amino acids and differ at just 16 amino-acid residues.

Putative regulatory sequences identified in the promoter region are the same and are highly conserved. However, significant differences exist in the 5' untranslated regions (UTR) of the transcribed sequences of these two genes, such as several deletions in the 5'-UTR of the H1(zero)-2 gene in comparison with the H1(zero)-1 gene 5'-UTR. The 3'-UTR is a short sequence of about 200 bp which is unexpected compared with the long 3'-UTR of mammalian H1(zero) mRNA, but it is in the same size range as in avian H5 mRNA.

Thus, the main differences between these two genes are observed in sequences potentially involved in the regulation of the H1(zero) gene expression such as the 5'-UTR. The two genes are expressed during embryogenesis and in several adult tissues. We discuss these findings in terms of the evolution of histone H1(zero) genes in vertebrates and the appearance of histone H5 in avian species.

KEY WORDS/PHRASES
CODING SEQUENCES
CONSERVED
EMBRYOGENESIS
GENE EXPRESSION
HISTONE
PROMOTER REGION
REGULATORY SEQUENCES
TRANSCRIBED SEQUENCES
UNTRANSLATED REGIONS

TITLE: THE MAMMALIAN SINGLE-MINDED (SIM) GENE: MOUSE cDNA STRUCTURE AND DIENCEPHALIC EXPRESSION INDICATE A CANDIDATE GENE FOR DOWN SYNDROME.
AUTHOR: YAMAKI A, NODA S, KUDOH J, SHINDOH N, MAEDA H, MINOSHIMA S, KAWASAKI K, SHIMIZU Y, SHIMIZU N
JOURNAL: GENOMICS 1996 Jul 1; 35(1):136-43
ABSTRACT: We have recently isolated a human homolog (hSIM) of the Drosophila single-minded (sim) gene from the Down syndrome critical region of chromosome 21 using the exon trapping method. The Drosophila sim gene encodes a transcription factor that regulates the development of the central nervous system midline cell lineage. To elucidate the structure of the mammalian SIM protein, we have isolated cDNA clones from a mouse embryo cDNA library. The cDNA clones encode a polypeptide of 657 amino acids with a bHLH (basic-helix-loop-helix) domain, characteristic of a large family of transcription factors, and a PAS (Per-Arnt-Sim) domain in the amino-terminal half region. Both of these domains have striking sequence homology with human SIM and Drosophila SIM proteins. In contrast, the carboxy-terminal half of the mouse SIM protein consists of a proline-rich region with no sequence homology to the Drosophila SIM protein. A similar proline-rich domain is known for the activator domain of a number of transcription factors. Whole-mount embryo in situ hybridization experiments revealed that the SIM mRNA is expressed prominently in the diencephalon of mouse embryos at 8-9.5 days postcoitum. The structural characteristics of the mouse SIM protein and its expression in the diencephalon during embryogenesis strongly suggest that the newly isolated mammalian SIM homolog may play a critical role in the development of the mammalian central nervous system. We propose that the human SIM gene may be one of the pathogenic genes of Down syndrome.

KEY WORDS/PHRASES
ACTIVATOR DOMAIN
cDNA CLONE
DOWN SYNDROME
EMBRYOGENESIS
EXON TRAPPING METHOD
EXPRESSION
HOMOLOG
PATHOGENIC GENES
POLYPEPTIDE
SEQUENCE HOMOLOGY
TRANSCRIPTION FACTOR

TITLE: PRIMARY STRUCTURE OF THE LONG AND SHORT SPLICE VARIANTS OF MOUSE COLLAGEN XII AND THEIR TISSUE-SPECIFIC EXPRESSION DURING EMBRYONIC DEVELOPMENT.
AUTHOR: BOHME K, LI Y, OH PS, OLSEN BR
JOURNAL: DEVELOPMENTAL DYNAMICS 1995 Dec; 204(4):432-45
ABSTRACT: Type XII collagen, a member of the FACIT group of extracellular matrix proteins, consists of molecules that are trimers of alpha1(XII) chains. cDNA cloning/sequencing of chicken alpha 1(XII) collagen and protein studies with mouse, bovine, and human material suggest that the alpha 1(XII) collagen gene gives rise to two molecular variants, differing in the length of the finger-like regions, by alternative splicing of the primary transcript. To provide a basis for studies of the function of the two variants in an organism that can be genetically manipulated, we have isolated and sequenced mouse cDNAs encoding both splice variants. The sequence provides the first complete nucleotide and amino acid sequence of mammalian type XII collagen. From these cDNAs we have generated digoxigenin-labeled RNA probes for in situ hybridization of developing mouse embryos to find out whether the splicing mechanism responsible for generation of the two forms is developmentally regulated. The results, combined with Northern blot and RT-PCR analysis of RNA from embryos at various developmental stages, demonstrate that the long form of collagenXII, XIIA, is the predominant form at early stages (ED7 and 11); at later stages of development (ED15 and 17) the short form, XIIB, becomes the major form. As the short form becomes the major product, the long splice variant continues to be expressed in several tissues, even after birth. An exception is dermis, which is positive for the long form up to embryonic day 15, but negative at day 18, when only the short form RNA can be detected.

KEY WORDS/PHRASES
COLLAGEN
EXTRACELLULAR MATRIX PROTEINS
MOLECULAR VARIANTS
NORTHERN BLOT
NUCLEOTIDE
PCR ANALYSIS
SITU HYBRIDIZATION
SEQUENCE
TRIMERS
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