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A capping enzyme (CE) is an enzyme that catalyzes the attachment of the 5' cap to messenger RNA molecules that are in the process of being synthesized in the cell nucleus during the first stages of gene expression. The addition of the cap occurs co-transcriptionally, after the growing RNA molecule contains as little as 25 nucleotides.
The preinitiation complex (PIC) is a large complex of proteins that is necessary for the transcription of protein-coding genes in eukaryotes and archaea.The PIC helps position RNA polymerase II over gene transcription start sites, denatures the DNA, and positions the DNA in the RNA polymerase II active site for transcription.
Unlike most DNA polymerases, it does not require a template. The preferred substrate of this enzyme is a 3'-overhang, but it can also add nucleotides to blunt or recessed 3' ends. Further, TdT is the only polymerase that is known to catalyze the synthesis of 2-15nt DNA polymers from free nucleotides in solution in vivo. [13]
The process of transcription is a major source of DNA damage, due to the formation of single-strand DNA intermediates that are vulnerable to damage. [53] The regulation of transcription by processes using base excision repair and/or topoisomerases to cut and remodel the genome also increases the vulnerability of DNA to damage.
The diphosphate 5' end then attacks the alpha phosphorus atom of a GTP molecule in order to add the guanine residue in a 5'5' triphosphate link. The enzyme (guanine-N 7-)-methyltransferase ("cap MTase") transfers a methyl group from S-adenosyl methionine to the guanine ring. [4] This type of cap, with just the (m 7 G) in position is called a ...
Restriction enzymes are endonucleases from eubacteria and archaea that recognize a specific DNA sequence. [3] The nucleotide sequence recognized for cleavage by a restriction enzyme is called the restriction site. Typically, a restriction site will be a palindromic sequence about four to six nucleotides long. Most restriction endonucleases ...
Deoxyribozymes, also called DNA enzymes, DNAzymes, or catalytic DNA, are DNA oligonucleotides that are capable of performing a specific chemical reaction, often but not always catalytic. This is similar to the action of other biological enzymes , such as proteins or ribozymes (enzymes composed of RNA ). [ 1 ]
Thus, acetylation of histones is known to increase the expression of genes through transcription activation. Deacetylation performed by HDAC molecules has the opposite effect. By deacetylating the histone tails, the DNA becomes more tightly wrapped around the histone cores, making it harder for transcription factors to bind to the DNA.