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Section: Genetics » Expression of Gene » Transcription in Prokaryotes and Eukaryotes
 
 
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  Transcription of yeast and plant mtDNA
 
     
 
Content
⇒ Expression of Gene : Protein Synthesis 2.  Transcription in Prokaryotes and Eukaryotes
⇒ Transcription in prokaryotes 
⇒ Single RNA polymerase in E. coli
⇒ Promoter sites for initiation of transcription in prokaryotes
⇒ Initiation and elongation of RNA synthesis in prokaryotes
⇒ 'Inchworm model' for elongation of transcript
⇒ Elongation arrest vs termination of transcription
⇒ Termination and antitermination of mRNA synthesis in prokaryotes
⇒ Transcription in eukaryotes 
⇒ Multiple RNA polymerases in eukaryotes
⇒ Promoter, enhancer and silencer sites for initiation of transcription in eukaryotes
⇒ Transcription factors and initiation of RNA synthesis in eukaryotes
⇒ Formation of preinitiation (transcription) complex with RNA polymerase II (Pol II)
⇒ Structure and role of TFIID and other transcription factors (TBP, TAFs)
⇒ TFIIB domains for interaction with TFIID/TATA complex
⇒ Phosphorylation of CTD of a subunit of Pol II
⇒ Formation of pre-initiation complex with Pol I and Pol III
⇒ Separate DNA binding and transcription activation domains
⇒ Transcription factors and elongation of RNA chains in eukaryotes
⇒ Chromatin structure and transcription
⇒ Transcription in mitochondria
⇒ Transcription of vertebrate mtDNA
⇒ Transcription of yeast and plant mtDNA
⇒ Transcription in chloroplasts
Transcription of yeast and plant mtDNA
The mtDNA in yeast is 78kbp and that in higher plants (master circle) is 200-240kbp, in contrast to a small (16-17kbp) mitochondrial genome in vertebrates. In yeast, mitochondrial genes are separated by extensive AT-rich non-coding spacer sequences; a bulk of mtDNA in higher plants is also non-coding. A 5S rRNA gene is a novel gene found only in plant mtDNA. In mtDNA of both yeast and higher plants, there are multiple transcription units, each with a separate promoter (unlike vertebrate mtDNA having a single promoter on each strand (LSP and HSP).

In higher plants, only 30%-70% of mtDNA is known to be transcribed, which gives rise to 20-30 polypeptides, 3 rRNA species and 15-20 tRNAs. Currently promoters of transcription units in higher plants mtDNA are being discovered. The RNA polymerases and the transcription factors associated with transcription of plant mtDNA, will be isolated and characterized during 1990s.

Most genes in plant mtDNA give monocistronic transcripts, although in some cases adjacent genes do give rise to dicistronic messages. (In chloroplasts of higher plants several polycistronic transcripts are produced). The transcription initiation sites are now known for many genes for plant mtDNAs. They contain a conserved CRTA (R = A or G) motif, although the degree of conservation is low, when compared with that in yeast.
 
     






     
     
 
 
     
 
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