Manidipa Mukhopadhyay

Bio: Manidipa Mukhopadhyay is an academic researcher from Bose Institute. The author has contributed to research in topics: Gene & Plasmid. The author has an hindex of 1, co-authored 1 publications receiving 10 citations.

Fine Tuning and Cross-talking of TGF-β Signal by Inhibitory Smads

Abstract: Transforming Growth Factor (TGF)-β family, including TGF-β, bone morphorgenic protein (BMP), and activn, plays an important role in essential cellular functions such as proliferation, differentiation, apoptosis, tissue remodeling, angiognesis, immune responses, and cell adhesions. TGF-β predominantly transmits the signals through serine/ threonine receptor kinases and cytoplasmic proteins called Smads. Since the discovery of TGF-β in the early 1980s, the dysregulation of TGF-β/Smad signaling has been implicated in the pathogenesis of human diseases. Among signal transducers in TGF-β/Smad signaling, inhibitory Smads (I-Smads), Smad6 and Smad7, act as major negative regulators forming autoinhibitory feedback loops and mediate the cross-talking with other signaling pathways. Expressions of I-Smads are mainly regulated on the transcriptional levels and post-translational protein degradations and their intracellular levels are tightly controlled to maintain the homeostatic balances. However, abnormal levels of I-Smads in the pathological conditions elicit the altered TGF-β signaling in cells, eventually causing TGF-β-related human diseases. Thus, exploring the molecular mechanisms about the regulations of ISmads may provide the therapeutic clues for human diseases induced by the abnormal TGF-β signaling.

A cytotoxic early gene of Bacillus subtilis bacteriophage SPO1.

Abstract: Some of the early genes of Bacillus subtilis bacteriophage SPO1 were hypothesized to function in the shutoff of host biosyntheses. Two of these genes, e3 and e22, were cloned and sequenced. E22 showed no similarity to any known protein, while E3, a highly acidic protein, showed significant similarity only to other similarly acidic proteins. Each gene was immediately downstream of a very active early promoter. Each was expressed actively during the first few minutes of infection and was then rapidly shut off and its RNA rapidly degraded. An e3 nonsense mutation severely retarded the degradation of e3 RNA. Expression of a plasmid-borne e3 gene, in either B. subtilis or Escherichia coli, resulted in the inhibition of host DNA, RNA, and protein syntheses and prevented colony formation. However, the e3 nonsense mutation caused no measurable decrease in either burst size or host shutoff during infection and, in fact, caused an increased burst size at high multiplicities of infection. We suggest that e3 is one of several genes involved in host shutoff, that its function is dispensable both for host shutoff and for phage multiplication, and that its shutoff function is not entirely specific to host activities.

The Bacteriophage λ DNA Replication Protein P Inhibits the oriC DNA- and ATP-binding Functions of the DNA Replication Initiator Protein DnaA of Escherichia coli

Abstract: Under the condition of expression of lambda P protein at lethal level, the oriC DNA-binding activity is significantly affected in wild-type E. coli but not in the rpl mutant. In purified system, the lambda P protein inhibits the binding of both oriC DNA and ATP to the wild-type DnaA protein but not to the rpl DnaA protein. We conclude that the lambda P protein inhibits the binding of oriC DNA and ATP to the wild-type DnaA protein, which causes the inhibition of host DNA synthesis initiation that ultimately leads to bacterial death. A possible beneficial effect of this interaction of lambda P protein with E. coli DNA initiator protein DnaA for phage DNA replication has been proposed.

The Mutation that Makes Escherichia coli Resistant to λ P Gene-mediated Host Lethality Is Located within the DNA Initiator Gene dnaA of the Bacterium

Abstract: Earlier, we reported that the bacteriophage lambda P gene product is lethal to Escherichia coli, and the E. coli rpl mutants are resistant to this lambda P gene-mediated lethality. In this paper, we show that under the lambda P gene-mediated lethal condition, the host DNA synthesis is inhibited at the initiation step. The rpl8 mutation maps around the 83 min position in the E. coli chromosome and is 94 % linked with the dnaA gene. The rpl8 mutant gene has been cloned in a plasmid. This plasmid clone can protect the wild-type E. coli from lambda P gene-mediated killing and complements E. coli dnaAts46 at 42 degrees C. Also, starting with the wild-type dnaA gene in a plasmid, the rpl-like mutations have been isolated by in vitro mutagenesis. DNA sequencing data show that each of the rpl8, rpl12 and rpl14 mutations has changed a single base in the dnaA gene, which translates into the amino acid changes N313T, Y200N, and S246T respectively within the DnaA protein. These results have led us to conclude that the rpl mutations, which make E. coli resistant to lambda P gene-mediated host lethality, are located within the DNA initiator gene dnaA of the host.

Phage Lambda P Protein: Trans-Activation, Inhibition Phenotypes and their Suppression

Abstract: The initiation of bacteriophage λ replication depends upon interactions between the oriλ DNA site, phage proteins O and P, and E. coli host replication proteins. P exhibits a high affinity for DnaB, the major replicative helicase for unwinding double stranded DNA. The concept of P-lethality relates to the hypothesis that P can sequester DnaB and in turn prevent cellular replication initiation from oriC. Alternatively, it was suggested that P-lethality does not involve an interaction between P and DnaB, but is targeted to DnaA. P-lethality is assessed by examining host cells for transformation by ColE1-type plasmids that can express P, and the absence of transformants is attributed to a lethal effect of P expression. The plasmid we employed enabled conditional expression of P, where under permissive conditions, cells were efficiently transformed. We observed that ColE1 replication and plasmid establishment upon transformation is extremely sensitive to P, and distinguish this effect from P-lethality directed to cells. We show that alleles of dnaB protect the variant cells from P expression. P-dependent cellular filamentation arose in ΔrecA or lexA[Ind-] cells, defective for SOS induction. Replication propagation and restart could represent additional targets for P interference of E. coli replication, beyond the oriC-dependent initiation step.