Transcription is the process of copying a segment of DNA into RNA. The segments of DNA transcribed into RNA molecules that can encode proteins are said to produce messenger RNA (mRNA). Other segments of DNA are copied into RNA molecules called non-coding RNAs (ncRNAs). mRNA comprises only 1–3% of total RNA samples. Less than 2% of the human genome can be transcribed into mRNA, while at least 80% of mammalian genomic DNA can be actively transcribed, with the majority of this 80% considered to be ncRNA.
RNA polymerase II is a multiprotein complex that transcribes DNA into precursors of messenger RNA (mRNA) and most small nuclear RNA (snRNA) and microRNA. It is one of the three RNAP enzymes found in the nucleus of eukaryotic cells. A 550 kDa complex of 12 subunits, RNAP II is the most studied type of RNA polymerase. A wide range of transcription factors are required for it to bind to upstream gene promoters and begin transcription.
IKBKAP is a human gene encoding the IKAP protein, which is ubiquitously expressed at varying levels in all tissue types, including brain cells. The IKAP protein is thought to participate as a sub-unit in the assembly of a six-protein putative human holo-Elongator complex, which allows for transcriptional elongation by RNA polymerase II. Further evidence has implicated the IKAP protein as being critical in neuronal development, and directs that decreased expression of IKAP in certain cell types is the molecular basis for the severe, neurodevelopmental disorder familial dysautonomia. Other pathways that have been connected to IKAP protein function in a variety of organisms include tRNA modification, cell motility, and cytosolic stress signalling. Homologs of the IKBKAP gene have been identified in multiple other Eukaryotic model organisms. Notable homologs include Elp1 in yeast, Ikbkap in mice, and D-elp1 in fruit flies. The fruit fly homolog (D-elp1) has RNA-dependent RNA polymerase activity and is involved in RNA interference.
In biology, the word gene can have several different meanings. The Mendelian gene is a basic unit of heredity and the molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protein-coding genes and non-coding genes.
DNA-directed RNA polymerases I, II, and III subunit RPABC1 is a protein that in humans is encoded by the POLR2E gene.
DNA-directed RNA polymerase II subunit RPB2 is an enzyme that in humans is encoded by the POLR2B gene.
DNA-directed RNA polymerases I, II, and III subunit RPABC3 is a protein that in humans is encoded by the POLR2H gene.
DNA-directed RNA polymerases I, II, and III subunit RPABC2 is a protein that in humans is encoded by the POLR2F gene.
DNA-directed RNA polymerase II subunit RPB9 is an enzyme that in humans is encoded by the POLR2I gene.
Upstream binding transcription factor (UBTF), or upstream binding factor (UBF), is a protein that in humans is encoded by the UBTF gene.
SON protein is a protein that in humans is encoded by the SON gene.
DNA polymerase delta subunit 2 is an enzyme that in humans is encoded by the POLD2 gene. It is a component of the DNA polymerase delta complex.
RNA-binding motif protein, Y chromosome, family 1 member A1/C is a protein that in humans is encoded by the RBMY1A1 gene.
Cleavage and polyadenylation specificity factor subunit 4 is a protein that in humans is encoded by the CPSF4 gene.
DNA primase large subunit is an enzyme that in humans is encoded by the PRIM2 gene.
DNA-directed RNA polymerase III subunit RPC10 is an enzyme that in humans is encoded by the POLR3K gene.
snRNA-activating protein complex subunit 1 is a protein that in humans is encoded by the SNAPC1 gene.
DNA-directed RNA polymerase III subunit RPC4 is an enzyme that in humans is encoded by the POLR3D gene.
Chloroplast DNA (cpDNA) is the DNA located in chloroplasts, which are photosynthetic organelles located within the cells of some eukaryotic organisms. Chloroplasts, like other types of plastid, contain a genome separate from that in the cell nucleus. The existence of chloroplast DNA was identified biochemically in 1959, and confirmed by electron microscopy in 1962. The discoveries that the chloroplast contains ribosomes and performs protein synthesis revealed that the chloroplast is genetically semi-autonomous. The first complete chloroplast genome sequences were published in 1986, Nicotiana tabacum (tobacco) by Sugiura and colleagues and Marchantia polymorpha (liverwort) by Ozeki et al. Since then, a great number of chloroplast DNAs from various species have been sequenced.
DNA polymerase alpha catalytic subunit is an enzyme that in humans is encoded by the POLA1 gene.
