The role of a Williams-Beuren syndrome-associated helix-loop-helix domain-containing transcription factor in activin/nodal signaling

We investigated the regulation of the activin/nodal-inducible distal element (DE) of the Xenopus goosecoid (gsc) promoter. On the basis of its interaction with the DE, we isolated a Xenopus homolog of the human Williams-Beuren syndrome critical region 11 (XWBSCR11), and further, show that it interacts with pathway-specific Smad2 and Smad3 in a ligand-dependent manner. Interestingly, we also find that XWBSCR11 functions cooperatively with FoxH1 (Fast-1) to stimulate DE-dependent transcription. We propose a mechanism in which FoxH1 functions together with Smads as a cofactor for the recruitment of transcription factors like XWBSCR11 in the process of activin/nodal-mediated gsc-specific induction. This mechanism provides considerable opportunities for modulation of transcription across a variety of activin/nodal-inducible genes, increasing diversity in promoter selection, thus leading to the differential induction of activin/nodal target genes.

The hydrogenase cytochrome b heme ligands of Azotobacter vinelandii are required for full H(2) oxidation capability

The hydrogenase in Azotobacter vinelandii, like other membrane-bound [NiFe] hydrogenases, consists of a catalytic heterodimer and an integral membrane cytochrome b. The histidines ligating the hemes in this cytochrome b were identified by H(2) oxidation properties of altered proteins produced by site-directed mutagenesis. Four fully conserved and four partially conserved histidines in HoxZ were substituted with alanine or tyrosine. The roles of these histidines in HoxZ heme binding and hydrogenase were characterized by O(2)-dependent H(2) oxidation and H(2)-dependent methylene blue reduction in vivo. Mutants H33A/Y (H33 replaced by A or Y), H74A/Y, H194A, H208A/Y, and H194,208A lost O(2)-dependent H(2) oxidation activity, H194Y and H136A had partial activity, and H97Y,H98A and H191A had full activity. These results suggest that the fully conserved histidines 33, 74, 194, and 208 are ligands to the hemes, tyrosine can serve as an alternate ligand in position 194, and H136 plays a role in H(2) oxidation. In mutant H194A/Y, imidazole (Imd) rescued H(2) oxidation activity in intact cells, which suggests that Imd acts as an exogenous ligand. The heterodimer activity, quantitatively determined as H(2)-dependent methylene blue reduction, indicated that the heterodimers of all mutants were catalytically active. H33A/Y had wild-type levels of methylene blue reduction, but the other HoxZ ligand mutants had significantly less than wild-type levels. Imd reconstituted full methylene blue reduction activity in mutants H194A/Y and H208A/Y and partial activity in H194,208A. These results indicate that structural and functional integrity of HoxZ is required for physiologically relevant H(2) oxidation, and structural integrity of HoxZ is necessary for full heterodimer-catalyzed H(2) oxidation.

An association between an aggrecan polymorphic allele and bilateral hand osteoarthritis in elderly white men: data from the Baltimore Longitudinal Study of Aging (BLSA)

OBJECTIVE

The aggrecan proteoglycan is a major component of articular cartilage and supports the biomechanical function of this tissue. A variable number tandem repeat (VNTR) polymorphism has been discovered recently in a region of the human aggrecan gene that codes for the chondroitin sulfate attachment sites. We examined whether alleles of this polymorphism displayed a non-random association with bilateral hand or knee osteoarthritis (OA) in men from the Baltimore Longitudinal Study of Aging (BLSA).

DESIGN

DNA was obtained from 93 Caucasian men, aged 60 and above, who had bilateral hand and standing knee radiographs read for changes of OA. The DNA was analyzed by polymerase chain reaction (PCR) and/or Southern blotting for the presence of the VNTR alleles.

RESULTS

Bilateral hand OA and knee OA were present in 46 and 30% of the men respectively. The following distribution of alleles was observed: allele 33 (0.5%), 29 (2.2%), 28 (31.7%), 27 (43.0%), 26 (16.7%), 25 (3.2%), 22 (2.2%) and 19 (0.5%). This distribution was similar to that detected in a random population of individuals from a separate study. In multiple logistic regression analysis, adjusting for age and body mass index, the presence of allele 27 was associated with bilateral hand OA with an odds ratio (OR) = 3.23 (95% confidence intervals (CI): 1.24-8.41). No other alleles showed an association with bilateral hand OA and the association between allele 27 and bilateral knee OA was not statistically significant (OR = 1.14; 95% CI: 0.45-2.88).

CONCLUSIONS

These data demonstrate the first association between a human aggrecan gene polymorphic allele and hand OA. This finding supports the concept that genetic factors may play a role in the development and/or progression of some forms of age-onset OA.

VirE1 protein mediates export of the single-stranded DNA-binding protein VirE2 from Agrobacterium tumefaciens into plant cells

Agrobacterium tumefaciens transfers single-stranded DNAs (T strands) into plant cells. VirE1 and VirE2, which is a single-stranded DNA binding protein, are important for tumorigenesis. We show that T strands and VirE2 can enter plant cells independently and that export of VirE2, but not of T strands, depends on VirE1.

Transmission of equine infectious anemia virus from horses without clinical signs of disease

Twenty seven adult horses positive to the agar gel immunodiffusion (AGID) test for equine infectious anemia (EIA), but with no history of clinical EIA, were used in transfusion studies to determine whether infectious EIA virus was present in 1 to 5 ml of their blood. Of 27 recipients, 21 (78%) became AGID test-positive at an average of 24 days after inoculation. Two horses that were initially negative when screened were retested and found to carry infectious virus in 5-300 ml of whole blood; the other 4 horses were not retested. Horse flies (Tabanus fuscicostatus Hine) were unable to transmit EIA virus from 10 AGID test-positive donors with no history of clinical EIA, but virus was transmitted from a pony with artificially induced acute EIA and from a horse that had recovered from a clinical attack of EIA 9 months earlier. Histopathologic changes indicative of EIA were noted in all test-positive recipients. The most consistent lesion was paracortical lymphoid hyperplasia in the splenic lymph node.