Biomedical subjects

Tadahiro Shimazu

Publications and source records attributed to Tadahiro Shimazu.

4 recordsLinked to original sources

PubMed2006

Multiple histone deacetylases and the CREB-binding protein regulate pre-mRNA 3'-end processing.

Trichostatin A (TSA), a specific inhibitor of histone deacetylases (HDACs), induces acetylation of various non-histone proteins such as p53 and alpha-tubulin. We purified several acetylated proteins by the affinity to an anti-acetylated lysine (AcLys) antibody from cells treated with TSA and identified them by mass spectrometry. Here we report on acetylation of CFIm25, a component of mammalian cleavage factor Im (CF Im), and poly(A) polymerase (PAP), a polyadenylating enzyme for the pre-mRNA 3'-end. The residues acetylated in these proteins were mapped onto the regions required for interaction with each other. Whereas CBP acetylated these proteins, HDAC1, HDAC3, HDAC10, SIRT1, and SIRT2 were involved in in vivo deacetylation. Acetylation of the CFIm25 occurred depending on the cleavage factor complex formation. Importantly, the interaction between PAP and CF Im complex was decreased by acetylation. We also demonstrated that acetylation of PAP inhibited the nuclear localization of PAP by inhibiting the binding to the importin alpha/beta complex. These results suggest that CBP and HDACs regulate the 3'-end processing machinery and modulate the localization of PAP through the acetylation and deacetylation cycle.

3' Untranslated Regions↗

PubMed2006

Self-activation of serine/threonine kinase AfsK on autophosphorylation at threonine-168.

A Hanks-type protein kinase AfsK autophosphorylates on threonine residue(s) and phosphorylates AfsR, a global regulator for secondary metabolism in Streptomyces coelicolor A3(2). Mass spectrometry of a tryptic digest of the autophosphorylated form of AfsK deltaC corresponding to the kinase catalytic domain (Met-1 to Arg-311) of AfsK, together with subsequent site-directed mutagenesis of the candidate amino acids, identified threonine-168 as a single autophosphorylation site. Threonine-168 is located in the activation loop that is known for some Ser/Thr kinases to modulate kinase activity on phosphorylation of one or more threonine residues within the loop. Consistent with this, mutant T168D, in which Thr-168 was replaced by Asp, became a constitutively active kinase; it phosphorylated AfsR to the same extent as AfsK deltaC produced in and purified from Escherichia coli cells during which a considerable population of it had been already phosphorylated intermolecularly. All these findings show that autophosphorylation or intermolecular phosphorylation of threonine-168 in AfsK accounts for the self-activation of its kinase activity.

Amino Acid Sequence↗

PubMed2003

Protein deacetylases: enzymes with functional diversity as novel therapeutic targets.

It is becoming increasingly clear that reversible acetylation of proteins is a signal directly controlling the activity of key cellular regulators. The enzymes controlling protein acetylation were identified as histone acetyltransferases (HATs) and histone deacetylases (HDACs). Following the discovery of HATs and HDACs, a number of non-histone proteins have been identified as substrates for these enzymes. HDACs play important roles in transcriptional regulation and pathogenesis of cancer through removing acetyl groups from histones and other transcriptional regulators. HDAC inhibitors case cell cycle arrest, differentiation and/or apoptosis of many tumors, suggesting their usefulness for chemotherapy and differentiation therapy. Since recent studies have revealed that HDACs are structurally and functionally diverse, it should be possible to develop inhibitors specific to individual HDACs as more promising agents for cancer therapy.

Acetylation↗

PubMed2002

In vivo destabilization of dynamic microtubules by HDAC6-mediated deacetylation.

Trichostatin A (TSA) inhibits all histone deacetylases (HDACs) of both class I and II, whereas trapoxin (TPX) cannot inhibit HDAC6, a cytoplasmic member of class II HDACs. We took advantage of this differential sensitivity of HDAC6 to TSA and TPX to identify its substrates. Using this approach, alpha-tubulin was identified as an HDAC6 substrate. HDAC6 deacetylated alpha-tubulin both in vivo and in vitro. Our investigations suggest that HDAC6 controls the stability of a dynamic pool of microtubules. Indeed, we found that highly acetylated microtubules observed after TSA treatment exhibited delayed drug-induced depolymerization and that HDAC6 overexpression prompted their induced depolymerization. Depolymerized tubulin was rapidly deacetylated in vivo, whereas tubulin acetylation occurred only after polymerization. We therefore suggest that acetylation and deacetylation are coupled to the microtubule turnover and that HDAC6 plays a key regulatory role in the stability of the dynamic microtubules.

Acetylation↗