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At least 289 records · Page 16Linked to original sources
PubMed1998

Regulation of extrinsic pathway factor Xa formation by tissue factor pathway inhibitor.

Tissue factor (TF) pathway inhibitor (TFPI) regulates factor X activation through the sequential inhibition of factor Xa and the VIIa.TF complex. Factor Xa formation was studied in a purified, reconstituted system, at plasma concentrations of factor X and TFPI, saturating concentrations of factor VIIa, and increasing concentrations of TF reconstituted into phosphatidylcholine:phosphatidylserine membranes (TF/PCPS) or PC membranes (TF/PC). The initial rate of factor Xa formation was equivalent in the presence or absence of 2.4 nM TFPI. However, reaction extent was small (<20%) relative to that observed in the absence of TFPI, implying the rapid inhibition of VIIa.TF during factor X activation. Initiation of factor Xa formation using increasing concentrations of TF/PCPS or TF/PC in the presence of TFPI yielded families of progress curves where both initial rate and reaction extent were linearly proportional to the concentration of VIIa.TF. These observations were consistent with a kinetic model in which the rate-limiting step represents the initial inhibition of newly formed factor Xa. Numerical analyses of progress curves yielded a rate constant for inhibition of VIIa.TF by Xa.TFPI (>10(8) M-1.s-1) that was substantially greater than the value (7.34 +/- 0.8 x 10(6) M-1.s-1) directly measured. Thus, VIIa.TF is inhibited at near diffusion-limited rates by Xa.TFPI formed during catalysis which cannot be explained by studies of the isolated reaction. We propose that the predominant inhibitory pathway during factor X activation may involve the initial inhibition of factor Xa either bound to or in the near vicinity of VIIa.TF on the membrane surface. As a result, VIIa.TF inhibition is unexpectedly rapid, and the concentration of active factor Xa that escapes regulation is linearly dependent on the availability of TF.

Animals↗
PubMed2001

The CGM1a (CEACAM3/CD66d)-mediated phagocytic pathway of Neisseria gonorrhoeae expressing opacity proteins is also the pathway to cell death.

Phagocytosis of Opa+ Neisseria gonorrhoeae (gonococcus, GC) by neutrophils is in part dependent on the interaction of Opa proteins with CGM1a (CEACAM3/CD66d) antigens, a neutrophil-specific receptor. However, the signaling pathways leading to phagocytosis have not been characterized. Here we show that interaction of OpaI bacteria with neutrophils or CGM1a-transfected DT40 cells induces calcium flux, which correlates with phagocytosis of bacteria. We identified an immunoreceptor tyrosine-based activation motif (ITAM) in CGM1a, and showed that the ability of CGM1a to transduce signals and mediate phagocytosis was abolished by mutation of the ITAM tyrosines. We also demonstrated that CGM1a-ITAM-mediated bacterial phagocytosis is dependent on Syk and phospholipase C activity in DT40 cells. Unexpectedly, the activation of the CGM1a-ITAM phagocytic pathway by Opa+ GC results in induction of cell death.

Amino Acid Sequence↗
PubMed2001

Novel cytoplasmic proteins of nontypeable Haemophilus influenzae up-regulate human MUC5AC mucin transcription via a positive p38 mitogen-activated protein kinase pathway and a negative phosphoinositide 3-kinase-Akt pathway.

Nontypeable Haemophilus influenzae (NTHi) is an important human pathogen that causes chronic otitis media with effusion (COME) in children and exacerbation of chronic obstructive pulmonary disease (COPD) in adults. Mucin overproduction, a hallmark of both diseases, has been shown to directly cause conductive hearing loss in COME and airway obstruction in COPD. The molecular mechanisms underlying mucin overproduction in NTHi infections still remain unclear. Here, we show that NTHi strongly up-regulates MUC5AC mucin transcription only after bacterial cell disruption. Maximal up-regulation is induced by heat-stable bacterial cytoplasmic proteins, whereas NTHi surface membrane proteins induce only moderate MUC5AC transcription. These results demonstrate an important role for cytoplasmic molecules from lysed bacteria in the pathogenesis of NTHi infections, and may well explain why many patients still have persistent symptoms such as middle ear effusion in COME after intensive antibiotic treatment. Furthermore, our results indicate that activation of p38 mitogen-activated protein kinase is required for NTHi-induced MUC5AC transcription, whereas activation of phosphoinositide 3-kinase-Akt pathway leads to down-regulation of NTHi-induced MUC5AC transcription via a negative cross-talk with p38 mitogen-activated protein kinase pathway. These studies may bring new insights into molecular pathogenesis of NTHi infections and lead to novel therapeutic intervention for COME and COPD.

Adult↗
PubMed1989

Growth factors, signaling pathways, and the regulation of proliferation and differentiation in BC3H1 muscle cells. I. A pertussis toxin-sensitive pathway is involved.

Cells of the nonfusing muscle cell line BC3H1 stop proliferating and express a family of muscle-specific proteins when the FBS concentration is reduced from 20 to 0.5% (Munson, R., K.L. Caldwell, and L. Glaser. 1982. J. Cell Biol. 92:350-356). Several growth factors have been shown to block differentiation in this cell line. To begin to investigate the potential role of G proteins in signal transducing pathways from these receptors, we have examined the effects of cholera toxin (CT) and pertussis toxin (PT) on proliferation and differentiation in BC3H1 cells. PT specifically ADP ribosylates a protein with an apparent molecular mass of 40 kD in BC3H1 cell membranes, whereas CT specifically ADP ribosylates three proteins of 35-43 kD. When added to exponentially growing cells in 20% FBS, CT and PT inhibited [3H]thymidine incorporation by up to 75% in a dose-dependent fashion. We found the synthesis of creatine kinase (CK) and skeletal muscle myosin light chain was reversibly induced in cells in 20% FBS treated with PT, but no increased synthesis was seen in cells treated with CT or in control cells; Northern analysis indicated this induction was at the level of mRNA. In cells shifted to 0.5% FBS, CT inhibited the normally induced synthesis of CK whereas PT potentiated it by approximately 50%. Forskolin also inhibited growth in 20% FBS and differentiation in 0.5% FBS medium in a dose-dependent fashion. both forskolin and CT elevated cAMP levels compared with control or PT-treated cells, suggesting that CT is blocking proliferation and differentiation by elevating cAMP levels. These results establish that a PT-sensitive pathway is involved in regulating proliferation and differentiation in BC3H1 cells, and we postulate that PT functions by ADP ribosylating a G protein that transduces signals from growth factor receptors in these cells.

Adenosine Diphosphate Ribose↗
PubMed1998

Activation of the MAP kinase pathway by FGF-1 correlates with cell proliferation induction while activation of the Src pathway correlates with migration.

FGF regulates both cell migration and proliferation by receptor-dependent induction of immediate-early gene expression and tyrosine phosphorylation of intracellular polypeptides. Because little is known about the disparate nature of intracellular signaling pathways, which are able to discriminate between cell migration and proliferation, we used a washout strategy to examine the relationship between immediate-early gene expression and tyrosine phosphorylation with respect to the potential of cells either to migrate or to initiate DNA synthesis in response to FGF-1. We demonstrate that transient exposure to FGF-1 results in a significant decrease in Fos transcript expression and a decrease in tyrosine phosphorylation of the FGFR-1, p42(mapk), and p44(mapk). Consistent with these biochemical effects, we demonstrate that attenuation in the level of DNA synthesis such that a 1.5-h withdrawal is sufficient to return the population to a state similar to quiescence. In contrast, the level of Myc mRNA, the activity of Src, the tyrosine phosphorylation of cortactin, and the FGF-1-induced redistribution of cortactin and F-actin were unaffected by transient FGF-1 stimulation. These biochemical responses are consistent with an implied uncompromised migratory potential of the cells in response to growth factor withdrawal. These results suggest a correlation between Fos expression and the mitogen-activated protein kinase pathway with initiation of DNA synthesis and a correlation between high levels of Myc mRNA and Src kinase activity with the regulation of cell migration.

3T3 Cells↗
PubMed1976

Alternative pathway of complement: recruitment of precursor properdin by the labile C3/C5 convertase and the potentiation of the pathway.

In this study the physiological role of properdin and the differential subunit composition of the solid phase enzymes of the pathway have been explored. Cell-bound C3 and C5 convertase differ in their C3b requirement. Apparently one molecule of C3b is sufficient to allow formation of C3 convertase (C3b,B), whereas two or more are required for generation of C5 convertase (C3bn,B). This conclusion was drawn from results indicating the critical role of the spacial distribution of C3b molecules on the cell surface in enzyme formation. While the C3/C5 convertase is fully capable of acting on C5 and thereby initiating the assembly of the cytolytic membrane attack complex, it is exceedingly labile and vulnerable to destruction by the C3b inactivator. It is the apparent role of properdin to confer a degree of stability upon the labile enzyme and to protect its C3 convertase function against enzymatic destruction. To achieve these effects, precursor properdin (pre-P) is recruited in a binding-activation reaction by the labile C3/C5 convertase. Multiple C3b molecules appear to be needed for the formation of properdin-activating principle. Three modes of regulation have been described, which involve spontaneous dissociation enzymatic degradation by C3b inactivator and disassembly by beta1H. The functional differences of pre-P and activated properdin (P) were delineated, pre-P displaying a weak affinity for C3b and P the capacity of strong interaction, P generating a soluble C3 convertase in serum and pre-P being unable to do so. Because of the profound differences between native pre-P and the laboratory product P, the question was raised as to whether soluble P represents an unphysiological form of the protein. On the basis of this and other studies, the conclusion was reached that in vitro properdin recruitment constitutes the terminal event of the properdin pathway, and that properdin augments the function of C3/C5 convertase without changing its substrate specificity.

Animals↗
PubMed2003

The synaptojanin-like protein Inp53/Sjl3 functions with clathrin in a yeast TGN-to-endosome pathway distinct from the GGA protein-dependent pathway.

Yeast TGN resident proteins that frequently cycle between the TGN and endosomes are much more slowly transported to the prevacuolar/late endosomal compartment (PVC) than other proteins. However, TGN protein transport to the PVC is accelerated in mutants lacking function of Inp53p. Inp53p contains a SacI polyphosphoinositide phosphatase domain, a 5-phosphatase domain, and a proline-rich domain. Here we show that all three domains are required to mediate "slow delivery" of TGN proteins into the PVC. Although deletion of the proline-rich domain did not affect general membrane association, it caused localization to become less specific. The proline-rich domain was shown to bind to two proteins, including clathrin heavy chain, Chc1p. Unlike chc1 mutants, inp53 mutants do not mislocalize TGN proteins to the cell surface, consistent with the idea that Chc1p and Inp53p act at a common vesicular trafficking step but that Chc1p is used at other steps also. Like mutations in the AP-1 adaptor complex, mutations in INP53 exhibit synthetic growth and transport defects when combined with mutations in the GGA proteins. Taken together with other recent studies, our results suggest that Inp53p and AP-1/clathrin act together in a TGN-to-early endosome pathway distinct from the direct TGN-to-PVC pathway mediated by GGA/clathrin.

ADP-Ribosylation Factors↗
PubMed2002

TNFalpha inhibits skeletal myogenesis through a PW1-dependent pathway by recruitment of caspase pathways.

Cachexia is associated with poor prognosis in patients with chronic disease. Tumor necrosis factor-alpha (TNFalpha) plays a pivotal role in mediating cachexia and has been demonstrated to inhibit skeletal muscle differentiation in vitro. It has been proposed that TNFalpha-mediated activation of NFkappaB leads to down regulation of MyoD, however the mechanisms underlying TNFalpha effects on skeletal muscle remain poorly understood. We report here a novel pathway by which TNFalpha inhibits muscle differentiation through activation of caspases in the absence of apoptosis. TNFalpha-mediated caspase activation and block of differentiation are dependent upon the expression of PW1, but occur independently of NFkappaB activation. PW1 has been implicated previously in p53-mediated cell death and can induce bax translocation to the mitochondria. We show that bax-deficient myoblasts do not activate caspases and differentiate in the presence of TNFalpha, highlighting a role for bax-dependent caspase activation in mediating TNFalpha effects. Taken together, our data reveal that TNFalpha inhibits myogenesis by recruiting components of apoptotic pathways through PW1.

Animals↗
PubMed2001

Bcl2-L-10, a novel anti-apoptotic member of the Bcl-2 family, blocks apoptosis in the mitochondria death pathway but not in the death receptor pathway.

By GenBank database searches and PCR, we have identified a novel human Bcl2-like gene, Bcl2-L-10, which contains conserved BH4, BH1 and BH2 domains but lacks BH3 domain. The Bcl2-L-10 gene has been assigned to chromosome 15q21.2. Transfection experiments demonstrated that Bcl2-L-10 can block apoptosis induced by interleukin-3 withdrawal and Bax expression, by prevention of cytochrome C release, caspase-3 activation and mitochondrial membrane potential collapse. Bcl2-L-10 cannot block TNFalpha-induced apoptosis. Furthermore, both the BH4 domain and the transmembrane domain of Bcl2-L-10 are necessary for its suppressive action on cell death. Our results demonstrated that Bcl2-L-10 is a newly detected anti-apoptotic member of the Bcl-2 family and that it blocks apoptosis in the mitochondrial death pathway but not in the death receptor pathway.

Amino Acid Sequence↗
PubMed1996

The metabolic pathway collection from EMP: the enzymes and metabolic pathways database.

The Enzymes and Metabolic Pathways database (EMP) is an encoding of the contents of over 10 000 original publications on the topics of enzymology and metabolism. This large body of information has been transformed into a queryable database. An extraction of over 1800 pictorial representations of metabolic pathways from this collection is freely available on the World Wide Web. We believe that this collection will play an important role in the interpretation of genetic sequence data, as well as offering a meaningful framework for the integration of many other forms of biological data.

Animals↗
PubMed1997

Stimulation of nitric oxide-cyclic guanosine monophosphate pathway in bovine ovarian theca cells by tumor necrosis factor alpha (TNF alpha). Is this pathway implicated in the TNF alpha-induced inhibition of luteinizing hormone-stimulated prorenin production?

Gonadal function is known to be controlled by many factors, including locally acting cytokines like tumor necrosis factor alpha (TNF alpha). One of the ways this cytokine acts is via the nitric oxide (NO)-cGMP pathway. Since we have shown that in the ovary theca cells are a target of TNF alpha's action, it was of interest to determine whether TNF alpha stimulates the NO-cGMP pathway in these cells and whether such a mechanism can be implicated in the observed TNF alpha-mediated inhibition of LH-stimulated prorenin synthesis and secretion. Treatment of isolated theca cells with TNF alpha resulted in a dose- and time-dependent increase in cGMP production. This increase was not detectable until 6 h after the addition of TNF alpha and was totally abolished by the protein synthesis inhibitor cycloheximide. Addition of either L-N6-nitroarginine methyl ester (L-NAME), an inhibitor of all three NO synthase (NOS) isoforms or 2-amino-5,6-dihydro-6-methyl-4H-1,3-thiazine (AMT), a specific inhibitor of the inducible isoform of the enzyme, likewise reversed the action of TNF alpha on cGMP formation. Finally, addition of 1H-[1,2,4]oxadiazolo [4,3-a] quinoxalin 1-one (ODQ), an inhibitor of NO-sensitive soluble guanylate cyclase, resulted in a concentration-dependent reduction of TNF alpha-stimulated cGMP formation. In contrast, the TNF alpha-mediated inhibition of LH-stimulated prorenin secretion was not affected by either L-NAME, AMT, or ODQ. Also the addition of stimulators of soluble guanylate cyclase, sodium nitroprusside, and S-nitroso-N-acetylpenicillamine, or 8 bromo-cGMP had no effect on the action of LH on theca cells. We conclude that although TNF alpha is able to stimulate cGMP formation in theca cells by inducing the expression of inducible NOS, the mechanism underlying the TNF alpha-mediated inhibition of LH-stimulated prorenin production is independent of its ability to induce cGMP formation.

Animals↗
PubMed1996

Flux limitations in the ortho pathway of benzoate degradation of Alcaligenes eutrophus: metabolite overflow and induction of the meta pathway at high substrate concentrations.

The growth behaviour of Alcaligenes eutrophus using various concentrations of benzoate was investigated. In batch culture, growth was exponential and growth rate (mu) and yields (Y) were high [mu = 0.51 h-1 and Yx/benzoate = 0.56 mol carbon (mol carbon)-1] when low concentrations of benzoate (< 5 mM) were used. These kinetic parameters were close to the maxima determined in a benzoate-limited chemostat [mu(max) = 0.55 h-1 and YX/benzoatemax = 0.57 mol carbon (mol carbon)-1] and the part of the energy for maintenance was limited (mATP = 4.3 +/- 2.2 mmol ATP g-1 h-1). When higher concentrations of benzoate were used (up to 40 mM), several metabolic limitations appeared. The specific rate of benzoate consumption was not altered, whereas growth was inhibited [Ki(benzoate) approximately 27 mM]. Furthermore, high concentrations of catechol together with some 1,2-dihydro-1,2-dihydroxybenzoate (DHB) transiently accumulated in the medium. The accumulation of catechol was attributed to limiting flux through catechol 1,2-dioxygenase estimated to be 5.2 mmol g-1 h-1, whereas that of DHB was provoked by an imbalance in the NADH/NAD+ intracellular content. The direct consequence of DHB accumulation was the induction of the meta pathway for the degradation of catechol, and this pathway contributed up to 20% of the total flux of catechol to the central metabolism. Finally, when very high concentrations of benzoate were used (55 mM), both growth and the specific rate of benzoate degradation were diminished due to a strong decrease in benzoate 1,2-dioxygenase specific activity.

Adenosine Triphosphate↗
PubMed2003

The ARG1-LIKE2 gene of Arabidopsis functions in a gravity signal transduction pathway that is genetically distinct from the PGM pathway.

The arl2 mutants of Arabidopsis display altered root and hypocotyl gravitropism, whereas their inflorescence stems are fully gravitropic. Interestingly, mutant roots respond like the wild type to phytohormones and an inhibitor of polar auxin transport. Also, their cap columella cells accumulate starch similarly to wild-type cells, and mutant hypocotyls display strong phototropic responses to lateral light stimulation. The ARL2 gene encodes a DnaJ-like protein similar to ARG1, another protein previously implicated in gravity signal transduction in Arabidopsis seedlings. ARL2 is expressed at low levels in all organs of seedlings and plants. arl2-1 arg1-2 double mutant roots display kinetics of gravitropism similar to those of single mutants. However, double mutants carrying both arl2-1 and pgm-1 (a mutation in the starch-biosynthetic gene PHOSPHOGLUCOMUTASE) at the homozygous state display a more pronounced root gravitropic defect than the single mutants. On the other hand, seedlings with a null mutation in ARL1, a paralog of ARG1 and ARL2, behave similarly to the wild type in gravitropism and other related assays. Taken together, the results suggest that ARG1 and ARL2 function in the same gravity signal transduction pathway in the hypocotyl and root of Arabidopsis seedlings, distinct from the pathway involving PGM.

Amino Acid Sequence↗
PubMed2002

Arabidopsis transcriptome profiling indicates that multiple regulatory pathways are activated during cold acclimation in addition to the CBF cold response pathway.

Many plants, including Arabidopsis, increase in freezing tolerance in response to low, nonfreezing temperatures, a phenomenon known as cold acclimation. Previous studies established that cold acclimation involves rapid expression of the CBF transcriptional activators (also known as DREB1 proteins) in response to low temperature followed by induction of the CBF regulon (CBF-targeted genes), which contributes to an increase in freezing tolerance. Here, we present the results of transcriptome-profiling experiments indicating the existence of multiple low-temperature regulatory pathways in addition to the CBF cold response pathway. The transcript levels of approximately 8000 genes were determined at multiple times after plants were transferred from warm to cold temperature and in warm-grown plants that constitutively expressed CBF1, CBF2, or CBF3. A total of 306 genes were identified as being cold responsive, with transcripts for 218 genes increasing and those for 88 genes decreasing threefold or more at one or more time points during the 7-day experiment. These results indicate that extensive downregulation of gene expression occurs during cold acclimation. Of the cold-responsive genes, 48 encode known or putative transcription factors. Two of these, RAP2.1 and RAP2.6, were activated by CBF expression and thus presumably control subregulons of the CBF regulon. Transcriptome comparisons indicated that only 12% of the cold-responsive genes are certain members of the CBF regulon. Moreover, at least 28% of the cold-responsive genes were not regulated by the CBF transcription factors, including 15 encoding known or putative transcription factors, indicating that these cold-responsive genes are members of different low-temperature regulons. Significantly, CBF expression at warm temperatures repressed the expression of eight genes that also were downregulated by low temperature, indicating that in addition to gene induction, gene repression is likely to play an integral role in cold acclimation.

Acclimatization↗
PubMed1985

Coupling between DNA replication and cell division mediated by the FtsA protein in Escherichia coli: a pathway independent of the SOS response, the "TER" pathway.

Inhibition of DNA synthesis prevented the recovery of cell division in filaments of D-3R [ftsA3(Ts) recA56] returned to the permissive temperature. The FtsA protein may be a signal involved in the "TER" pathway, a series of events that coordinate cell division with DNA replication, that is independent of the SOS pathway.

Bacterial Proteins↗
PubMed1997

Cytochrome c terminal oxidase pathways of Azotobacter vinelandii: analysis of cytochrome c4 and c5 mutants and up-regulation of cytochrome c-dependent pathways with N2 fixation.

The Azotobacter vinelandii cytochrome c5 gene (termed cycB) was cloned and sequenced. Mutants in this c-type cytochrome as well as cytochrome c4 mutants (mutations in cycA) and double mutants in both of the c-type respiratory pathways were characterized. Spectral and heme staining experiments on membranes from the mutants were consistent with the anticipated characteristics of all the gene-directed mutants. Membranes of the individual cytochrome c4 or c5 mutants had normal respiratory rates with physiological substrates but respiration significantly lower than the wild-type rate with ascorbate-N,N,N',N',-tetramethyl-p-phenylenediamine (TMPD) as a reductant. The growth rates of the individual cytochrome c4 or c5 mutants were not markedly different from that of the wild-type strain, but the cycA cycB double-mutant strain was noticeably growth retarded at and below 7.5% O2 on both N-containing and N-free media. The double-mutant strain was unable to grow on agar plates at O2 tensions of 2.5% or less on N-free medium. As the wild-type growth was unaffected by varying the O2 tension, the results indicate that the role of the cytochrome c-dependent pathways is to provide respiration at intermediate (5 to 10%) and low (below 5%) O2 tensions. The two c-type cytochrome genes are transcriptionally up-regulated with N2 fixation; N starvation caused 2.8-fold and 7- to 10-fold increases in the promoter activities of cycA and cycB, respectively, but these activities were affected little by the O2 level supplied to the cultures.

Amino Acid Sequence↗
PubMed1999

A functional 4-hydroxysalicylate/hydroxyquinol degradative pathway gene cluster is linked to the initial dibenzo-p-dioxin pathway genes in Sphingomonas sp. strain RW1.

The bacterium Sphingomonas sp. strain RW1 is able to use dibenzo-p-dioxin, dibenzofuran, and several hydroxylated derivatives as sole sources of carbon and energy. We have determined and analyzed the nucleic acid sequence of a 9,997-bp HindIII fragment downstream of cistrons dxnA1A2, which encode the dioxygenase component of the initial dioxygenase system of the corresponding catabolic pathways. This fragment contains 10 colinear open reading frames (ORFs), apparently organized in one compact operon. The enzymatic activities of some proteins encoded by these genes were analyzed in the strain RW1 and, after hyperexpression, in Escherichia coli. The first three ORFs of the locus, designated dxnC, ORF2, and fdx3, specify a protein with a low homology to bacterial siderophore receptors, a polypeptide representing no significant homology to known proteins, and a putative ferredoxin, respectively. dxnD encodes a 69-kDa phenol monooxygenase-like protein with activity for the turnover of 4-hydroxysalicylate, and dxnE codes for a 37-kDa protein whose sequence and activity are similar to those of known maleylacetate reductases. The following gene, dxnF, encodes a 33-kDa intradiol dioxygenase which efficiently cleaves hydroxyquinol, yielding maleylacetate, the ketoform of 3-hydroxy-cis,cis-muconate. The heteromeric protein encoded by dxnGH is a 3-oxoadipate succinyl coenzyme A (succinyl-CoA) transferase, whereas dxnI specifies a protein exhibiting marked homology to acetyl-CoA acetyltransferases (thiolases). The last ORF of the sequenced fragment codes for a putative transposase. DxnD, DxnF, DxnE, DxnGH, and DxnI (the activities of most of them have also been detected in strain RW1) thus form a complete 4-hydroxysalicylate/hydroxyquinol degradative pathway. A route for the mineralization of the growth substrates 3-hydroxydibenzofuran and 2-hydroxydibenzo-p-dioxin in Sphingomonas sp. strain RW1 thus suggests itself.

Acetyl-CoA C-Acetyltransferase↗
PubMed2000

Cross-pathway regulation in Saccharomyces cerevisiae: activation of the proline utilization pathway by Ga14p in vivo.

The Put3p and Gal4p transcriptional activators are members of a distinct class of fungal regulators called the Cys(6) Zn(II)(2) binuclear cluster family. This family includes over 50 different Saccharomyces cerevisiae proteins that share a similar domain organization. Gal4p activates the genes of the galactose utilization pathway permitting the use of galactose as the sole source of carbon and energy. Put3p controls the expression of the proline utilization pathway that allows yeast cells to grow on proline as the sole nitrogen source. We report that Gal4p can activate the PUT structural genes in a strain lacking Put3p. We also show that the activation of PUT2 by Gal4p depends on the presence of the inducer galactose and the Put3p binding site and that activation increases with increased dosage of Gal4p. Put3p cannot activate the GAL genes in the absence of Gal4p. Our in vivo results confirm previously published in vitro data showing that Gal4p is more promiscuous than Put3p in its DNA binding ability. The results also suggest that under appropriate circumstances, Gal4p may be able to function in place of a related family member to activate expression.

DNA-Binding Proteins↗