Showing papers by "Narendra Tuteja published in 2000"
TL;DR: Ku seems to be a multifunctional protein that has been implicated to be involved directly or indirectly in many important cellular metabolic processes such as DNA double-strand break repair, V(D)J recombination of immunoglobulins and T-cell receptor genes, Immunoglobulin isotype switching, DNA replication, transcription regulation, regulation of heat shock-induced responses, and regulation of the precise structure of telomeric termini.
Abstract: Ku is a heterodimeric protein composed of approximately 70- and approximately 80-kDa subunits (Ku70 and Ku80) originally identified as an autoantigen recognized by the sera of patients with autoimmune diseases. Ku has high binding affinity for DNA ends and that is why originally it was known as a DNA end binding protein, but now it is known to also bind the DNA structure at nicks, gaps, hairpins, as well as the ends of telomeres. It has been reported also to bind with sequence specificity to DNA and with weak affinity to RNA. Ku is an abundant nuclear protein and is present in vertebrates, insects, yeast, and worms. Ku contains ssDNA-dependent ATPase and ATP-dependent DNA helicase activities. It is the regulatory subunit of the DNA-dependent protein kinase that phosphorylates many proteins, including SV-40 large T antigen, p53, RNA-polymerase II, RP-A, topoisomerases, hsp90, and many transcription factors such as c-Jun, c-Fos, oct-1, sp-1, c-Myc, TFIID, and many more. It seems to be a multifunctional protein that has been implicated to be involved directly or indirectly in many important cellular metabolic processes such as DNA double-strand break repair, V(D)J recombination of immunoglobulins and T-cell receptor genes, immunoglobulin isotype switching, DNA replication, transcription regulation, regulation of heat shock-induced responses, regulation of the precise structure of telomeric termini, and it also plays a novel role in G2 and M phases of the cell cycle. The mechanism underlying the regulation of all the diverse functions of Ku is still obscure.
185 citations
TL;DR: The results suggest that pea DNA helicase could be an important multifunctional protein involved in protein synthesis, maintaining the basic activities of the cell, and in upregulation of topoisomerase I activity.
Abstract: DNA helicases play an essential role in all aspects of nucleic acid metabolism, by providing a duplex-unwinding function. This is the first report of the isolation of a cDNA (1.6 kb) clone encoding functional DNA helicase from a plant (pea, Pisum sativum). The deduced amino-acid sequence has eight conserved helicase motifs of the DEAD-box protein family. It is a unique member of this family, containing DESD and SRT motifs instead of DEAD/H and SAT. The encoded 45.5 kDa protein has been overexpressed in bacteria and purified to homogeneity. The purified protein contains ATP-dependent DNA and RNA helicase, DNA-dependent ATPase, and ATP-binding activities. The protein sequence contains striking homology with eIF-4A, which has not so far been reported as DNA helicase. The antibodies against pea helicase inhibit in vitro translation. The gene is expressed as 1.6 kb mRNA in different organs of pea. The enzyme is localized in the nucleus and cytosol, and unwinds DNA in the 3' to 5' direction. The pea helicase interacts with pea topoisomerase I protein and stimulates its activity. These results suggest that pea DNA helicase could be an important multifunctional protein involved in protein synthesis, maintaining the basic activities of the cell, and in upregulation of topoisomerase I activity. The discovery of such a protein with intrinsic multiple activity should make an important contribution to our better understanding of DNA and RNA transactions in plants.
90 citations
TL;DR: The current findings provide the first hint of a role for ribosomal protein S29 in the apoptotic process as assessed by various morphological and biochemical characteristics, including cell shrinkage, chromatin condensation, membrane blebbing, formation of apoptotic bodies, TUNEL, FACS, and internucleosomal DNA fragmentation.
45 citations
TL;DR: Helicases are ubiquitous enzymes that catalyze the unwinding of energetically stable duplex DNA (DNA helicases) or duplex RNA secondary structures (RNA helicases), and thus play essential role in all aspects of nucleic acid metabolism as mentioned in this paper.
Abstract: Helicases are ubiquitous enzymes that catalyze the unwinding of energetically stable duplex DNA (DNA helicases) or duplex RNA secondary structures (RNA helicases) and thus play essential role in all aspects of nucleic acid metabolism. All helicases share the common property of being able to use the energy derived from NTP hydrolysis (usually ATP) to break the hydrogen bonds that hold both the two strands together. Mechanistically, there are two classes of helicases: those that can translocate 3′- to 5′-, or 5′- to 3′- directions with respect to the strand on which they initially bind. DNA helicases are essential for key biological processes such as the DNA replication, repair, recombination, and transcription. Similarly, RNA helicases represent a large family of proteins that are involved in modulation of RNA structure and thereby influencing RNA synthesis, splicing, replication, translation initiation, editing, rRNA processing, ribosome assembly, nuclear mRNA export, mRNA stabilization, and degr...
22 citations