B Family (b + family)

Distribution by Scientific Domains

Selected Abstracts

Two conserved domains in regulatory B subunits mediate binding to the A subunit of protein phosphatase 2A

FEBS JOURNAL, Issue 2 2002
Xinghai Li
Protein phosphatase 2A (PP2A) is an abundant heterotrimeric serine/threonine phosphatase containing highly conserved structural (A) and catalytic (C) subunits. Its diverse functions in the cell are determined by its association with a highly variable regulatory and targeting B subunit. At least three distinct gene families encoding B subunits are known: B/B55/CDC55, B,/B56/RTS1 and B,/PR72/130. No homology has been identified among the B families, and little is known about how these B subunits interact with the PP2A A and C subunits. In vitro expression of a series of B56, fragments identified two distinct domains that bound independently to the A subunit. Sequence alignment of these A subunit binding domains (ASBD) identified conserved residues in B/B55 and PR72 family members. The alignment successfully predicted domains in B55 and PR72 subunits that similarly bound to the PP2A A subunit. These results suggest that these B subunits share a common core structure and mode of interaction with the PP2A holoenzyme. [source]

Human disease resulting from gene mutations that interfere with appropriate nuclear factor-,B activation

Jordan S. Orange
Summary:, The nuclear factor (NF)-,B family of transcription factors serves vital roles in a wide array of cell functions. An increasing number of human genetic lesions that result in defined disease entities are linked to inappropriate activation of NF-,B. The resulting aberrant NF-,B function can lead to cellular defects that ultimately impair normal developmental processes, host immune defenses, or both. Molecular defects that lie upstream in cell-signaling pathways and rely upon NF-,B activation tend to give a more specific phenotype, whereas those closer to the actual NF-,B proteins have broader defects. A detailed study of these diseases can provide insight into the biochemistry of NF-,B activation as well as the role of NF-,B in human health. [source]

Transcription factors NF-,B and Sp1 are major determinants of the basal promoter activity of the rat GD3-synthase gene

G. Zeng
GD3-synthase is one of the key sialyltransferases responsible for synthesis of ganglioside GD3, the substrate for initiation of the ,b' and ,c' series ganglioside synthesis. We have previously cloned the rat GD3-synthase gene promoter, and preliminary characterization has identified a minimal 0.5-kb region that has a strong basal promoter activity, and is GC-rich and has no CAAT or TATA boxes. In this study, we showed that the Sp1 and NF-,B sites in this region significantly contributed to basal GD3-synthase promoter activity. When either the Sp1 or NF-,B sites were deleted, a 50% decrease in promoter activity was observed. The same results were obtained by a decoy strategy using oligonucleotides containing the Sp1 or NF-,B sites. The binding to the Sp1 and NF-,B sites was confirmed by electrophoretic mobility shift assay (EMSA), competition and supershift EMSA. In addition, cell-type specific activation of the promoter was also determined. The promoter was highly activated in the GD3-expressing F-11 cells while repressed in NG-108 cells in which GD3 is almost undetectable. An additional band of NF-,B family was identified only in the F-11 nuclear extract using the NF-,B consensus probe by EMSA. DNA pull-down assays were further carried out to screen proteins that bound to the promoter including the basal region and the potential negative-regulatory region between ,526 and ,769. More than 10 major binding proteins were pulled down, some of which were present only in the F-11 or NG-108 nuclear extracts. Our data demonstrate that NF-,B and Sp1 are the major determinants for the basal promoter activity and some factors such as NF-,B may be involved in cell type-specific expression of the gene. [source]

Proinflammatory phenotype with imbalance of KLF2 and RelA: Risk of childhood stroke with sickle cell anemia,

Judy Enenstein
Altered inflammation signaling within the cerebral vasculature may be an important risk factor for stroke in children with sickle cell anemia (SCA). This study examines how differential expression of NF,B/p65 (RelA), KLF2, and other transcription factors may act as switches in inflammation signaling leading to observed differences between non-SCA (NS) African Americans and African Americans with SCA who are either at risk (AR) or not at risk (NAR) of childhood stroke based on occurrence of Circle of Willis disease. Clover/Transfac analysis was used to identify overrepresented transcription factor binding motifs on genes associated with inflammation. Transcription factor binding motifs for the NF,B family and RFX1 were overrepresented on inflammation signaling gene set analysis. Variations in protein expression were determined by flow cytometry of blood outgrowth endothelial cells (BOECs) from NS, AR, and NAR donors and Western blots of protein extracts from both unstimulated and TNF,/IL1,-stimulated BOECs. BOECs from patients with SCA had more cytoplasmic-derived RelA compared with NS BOECs. Sickle BOECs also had heightened responses to inflammatory stimuli compared with NS BOECs, as shown by increased nuclear RelA, and intracellular adhesion molecule (ICAM) response to TNF,/IL1, stimulation. Multiple control points in RelA signaling were associated with risk of childhood stroke. The ratio of proinflammatory factor RelA to anti-inflammatory factor KLF2 was greater in BOECs from AR donors than NS donors. Group risk of childhood stroke with SCA was greatest among individuals who exhibited increased expression of proinflammatory transcription factors and decreased expression of transcription factors that suppress inflammation. Am. J. Hematol. 2010. 2009 Wiley-Liss, Inc. [source]

Expression, purification, crystallization and preliminary X-ray analysis of a nucleoside kinase from the hyperthermophile Methanocaldococcus jannaschii

Linda Arnfors
Methanocaldococcus jannaschii nucleoside kinase (MjNK) is an ATP-dependent non-allosteric phosphotransferase that shows high catalytic activity for guanosine, inosine and cytidine. MjNK is a member of the phosphofructokinase B family, but participates in the biosynthesis of nucleoside monophosphates rather than in glycolysis. MjNK was crystallized as the apoenzyme as well as in complex with an ATP analogue and Mg2+. The latter crystal form was also soaked with fructose-6-phosphate. Synchrotron-radiation data were collected to 1.70, for the apoenzyme crystals and 1.93, for the complex crystals. All crystals exhibit orthorhombic symmetry; however, the apoenzyme crystals contain one monomer per asymmetric unit whereas the complex crystals contain a dimer. [source]

Solid-Phase Synthesis of Dihydrovirginiamycin S1, a Streptogramin B Antibiotic

Alex Shaginian
Abstract We describe the first solid-phase synthesis of dihydrovirginiamycin S1, a member of the streptogramin B family of antibiotics, which are nonribosomal-peptide natural products produced by Streptomyces. These compounds, along with the synergistic group A components, are "last line of defense" antimicrobial agents for the treatment of life-threatening infections such as vancomycin-resistant enterococci. The synthesis features an on-resin cyclization and is designed to allow production of streptogramin B analogues with diversification at positions 1,, 1, 2, 3, 4, and 6. Several synthetic challenges known to hinder the synthesis of this class of compounds were solved, including sensitivity to acids and bases, and epimerization and rearrangements, through the judicious choice of deprotection conditions, coupling conditions, and synthetic strategy. This work should enable a better understanding of structure,activity relationships in the streptogramin B compounds, possible identification of analogues that bypass known resistance mechanisms, and perhaps the identification of analogues with novel biological activities. [source]

Comparative genomics of the Mill family: a rapidly evolving MHC class,I gene family

Yutaka Watanabe
Abstract Mill (MHC class,I-like located near the leukocyte receptor complex) is a novel family of class,I genes identified in mice that is most closely related to the human MICA/B family. In the present study, we isolated Mill cDNA from rats and carried out a comparative genomic analysis. Rats have two Mill genes orthologous to mouse Mill1 and Mill2 near the leukocyte receptor complex, with expression patterns similar to those of their mouse counterparts. Interspecies sequence comparison indicates that Mill is one of the most rapidly evolving class,I gene families and that non-synonymous substitutions occur more frequently than synonymous substitutions in its ,,1 domain, implicating the involvement of Mill in immune defenses. Interestingly, the ,,2 domain of rat Mill2 contains a premature stop codon in many inbred strains, indicating that Mill2 is not essential for survival. A computer search of the database identified a horse Mill -like expressed sequence tag, indicating that Mill emerged before the radiation of mammals. Hence, the failure to find Mill in human indicates strongly that it was lost from the human lineage. Our present work provides convincing evidence that Mill is akin to the MICA/B family, yet constitutes a distinctgene family. [source]