Biomedical subjects

B deCrombrugghe

Publications and source records attributed to B deCrombrugghe.

5 recordsLinked to original sources

PubMed1999

Physical and genetic interactions between Alx4 and Cart1.

Alx4 and Cart1 are closely related members of the family of transcription factors that contain the paired-type homeodomain. In contrast to other types of homeodomains, the paired-type homeodomain has been shown to mediate high-affinity sequence-specific DNA binding to palindromic elements as either homodimers or as heterodimers with other family members. Alx4 and Cart1 are co-expressed at several sites during development, including the craniofacial mesenchyme, the mesenchymal derivatives of neural crest cells in the first branchial arch and the limb bud mesenchyme. Because of the molecular similarity and overlapping expression pattern, we have analyzed the functional and genetic relationships between Alx4 and Cart1. The two proteins have similar DNA-binding activity in vitro and can form DNA-binding heterodimers; furthermore, they activate transcription of reporter genes that contain high-affinity DNA-binding sites in cell culture in a similar manner. Therefore, at least by these criteria, the two proteins are functionally redundant. Analysis of double mutant animals reveals several genetic interactions. First, mutation of Cart1 exacerbates Alx4-dependent polydactyly in a manner that is dependent on gene dosage. Second, there are complex genetic interactions in the craniofacial region that reveal a role for both genes in the fusion of the nasal cartilages and proper patterning of the mandible, as well as other craniofacial structures. Third, double mutant mice show a split sternum that is not detected in mice with any other genotype. Interpreted in the context of the biochemical characterization, the genetic analysis suggests that Alx4 and Cart1 are indeed functionally redundant, and reveal both unique and redundant functions for these genes in development.

Animals↗

PubMed1996

The role of type X collagen in endochondral ossification as deduced by Fourier transform infrared microscopy analysis.

Type X collagen has been implicated in the morphogenetic events of endochondral ossification (EO), including the calcification of hypertrophic cartilage and trabeculae prior to their replacement by bone and marrow. Recently, transgenic mice which expressed a truncated collagen X protein were reported to exhibit morphologic alterations in all tissues arising through EO. Fourier Transform InfraRed (FTIR) spectroscopy has previously been shown to provide quantitative and qualitative information about the relative amount of mineral and carbonate present, mineral composition, and crystal perfection. To determine the role of collagen X in mineralization, the "quality" of mineral crystals was analyzed in thin sections of calcified cartilage from tibia obtained from several independent transgenic mouse lines showing varying degrees of the mutant phenotype and mice without type X collagen expression, by means of Fourier Transform InfraRed microscopy (FTIRM). In the present paper, the term "mineral quality" is employed to describe crystallinity/crystal maturation, and acid phosphate content. The results indicate significant differences between normal and transgenic mice bone mineral, both in the amount present and the "quality" of the crystals. In contrast, the analysis of the mineral in mice without type X collagen expression was not different from their age/sex-matched controls.

Animals↗

PubMed1980

Molecular mechanism for the capture and excision of the transforming gene of avian sarcoma virus as suggested by analysis of recombinant clones.

Structural analysis of two cDNA clones, derived from reverse transcripts of avian sarcoma virus 21S mRNA's, reveals unusual features in the organization and expression of the integrated avian sarcoma virus (ASV) proviral DNA and predicts a mechanism for recombination events that will lead to either the capture or the excision of the transforming gene of this virus. The latter is supported by our observation that there is an extensive homologous region on either side of the transforming gene that will allow site-specific deletion or integration to occur. Comparison of the clone derived from the src-specific 21S mRNA coding for the transforming gene product to that derived from the env-specific 21S mRNA coding for the envelope glycoprotein show that the common c region present at the 3' terminus of the ASV genome is 326 bases long. Within this c region are nucleotide sequences that may play key roles in the life cycle of this virus. These regulatory sequences include (i) probable promoter sites for the initiation of transcription, (ii) a polyadenylation signal, and (iii) a sequence that is complementary to the 3' termini of both the env and the src regions, which will allow the generation of transformation-defective deletions.

Avian Sarcoma Viruses↗

PubMed1975

Termination of transcription in bacteriophage lambda. Heterogeneous, 3'-terminal oligo-adenylate additions and the effects of rho factor.

RNA transcripts were synthesized in vitro from a lambda DNA template with purified Escherichia coli RNA polymerase either in the presence or absence of the protein termination factor, rho. The products were initially characterized by electrophoresis on polyacrylamide slab gels, and two of the lower molecular weight discrete species (6 S and 4 S RNA) were further characterized by standard two-dimensional "fingerprint" analysis. Production of the 4 S RNA was strongly affected by the presence of rho, whereas production of the 6 S RNA species was relatively unaffected by rho. 3'-Terminal oligonucleotide fragments were then selectively isolated on columns of dihydroxyboryl-substituted cellulose from these transcripts. Sequence analysis of these oligonucleotide products indicated: (a) that all of the transcripts examined possess similar degrees of 3'-terminal sequence heterogeneity which consisted predominantly of the addition of 1 to 5 adenylate residues to the 3'-terminus of the transcript; and (b) that rho factor-enhanced termination results in a definite structural change in the nucleotide sequence with which an RNA molecule can terminate.

Adenine Nucleotides↗

PubMed1970

Cyclic AMP receptor protein of E. coli: its role in the synthesis of inducible enzymes.

A cyclic AMP binding protein has been purified over 100-fold from E. coli extracts. Protein purified from wild-type strains binds cyclic AMP with an apparent dissociation constant of 1-2 x 10(-6)M. Two mutant strains that are unresponsive to exogenous cyclic AMP have altered binding activity; the protein purified from one of these mutants has a decreased affinity for cyclic AMP (apparent dissociation constant = 2 x 10(-5)M). Extracts of this mutant are deficient in their ability to support beta-galactosidase synthesis in vitro. The addition of purified, wild-type binding protein to these extracts restores enzyme synthesis toward normal. Because this binding protein appears to be required for cyclic AMP action, we suggest it be called the cyclic AMP receptor protein (CR protein).

Adenine Nucleotides↗