Archaeal regulation Flashcards
What are the three groups of archaea and what does the main one we know of consist of?
Euarchaea: halophiles, acidophiles, methanogens etc.
Crenarchaea
Thaumarchaea
What was the initial classification of the domains of life and who destroyed that initial narrative?
The initial classification of the domains was that protists (prokaryotes) gave rise to the more complex eukaryotes. Then came Carl Woese, who used rRNA as a taxonomic marker (instead of just morphology) and classified life into prokaryotes, archaea and eukaryotes.
What are the archaeas called that we believe are most closely related to eukaryotes?
Asgard archaea.
What are some unique features of archaea?
Phospholipids in membrane are linked together by ether instead of lipids.
They don’t have any fatty acids.
They have very unique viruses, and the diversity is higher than within eukaryotes and bacteria.
Multiple OriCs
In what ways are archaea similar to bacteria?
They have operons.
Don’t have introns.
Don’t have nucleus.
Quite small.
In what ways are archaea similar and different from eukaryotes?
Similarities: both archaea and eukaryotes have a cytoskeleton, which bacteria don’t. Both lack true peptidoglycan in the membrane, which bacteria has. Both eukaryotes and archaea have nuclesomes and histones.
Differences: Archaea and bacteria are in many ways morphologically more similar to each other. Archean genome don’t have introns or a nucleus, but have operons like bacteria.
What does the genome look like in archaea? Is the organization more similar to bacteria or eukaryotes?
Circular, lacking of introns and organized into operons, like bacterial genomes. The chromosome contains multiple origins of replication, instead of only one (like in bacteria).
Both histones and nucleosomes are present in archaea, which is more similar to eukaryotes.
What is the purpose of having multiple origins of replication (archaea)?
The genes that are used the most are located closer to the origins of replication, because they are expressed in higher levels. For example housekeeping genes, core metabolic genes and tRNA genes.
What are the two main ways of chromosome organization in archaea?
Eukaryotic like histones: histones in archaea that are homologous to eukaryotic histones, but they lack N and C terminals. More present in Euryarchaea.
Small-DNA binding proteins: proteins that bind DNA and whose concentration affects the accessibility and structure of the DNA. More present in Crenarchaea.
What is Alba? Where can it be found?
Alba is a small DNA binding protein and affects the structure of DNA. Acetylation and deacetylation, as well as the concentration of Alba, affects the accessibility. Loops form in the DNA. Highly abundant in crenarchaea and less abundant in euryarchaea.
How can Alba be modified?
By acetylation or deacetylation.
Acetylation: decreased DNA binding –> less loops.
Deacetylation: increased DNA binding –> more loops.
How is euryarchaea DNA organized?
Histones homologous to eukaryotic histones are present, and Alba protein creates loops.
How is crenarchaea DNA organized?
Don’t have histones, but Alba protein creates different structures depending on the concentration.
What does the promoter of archaea look like? More bacterial or eukaryotic?
More eukaryotic. Contains a TATA box and a BRE (TFIIB recognition element) upstreams, and Inr (initiator) downstream of the TATA and a DPE downstream of the Inr.
Is mRNA capping and polyadenylation present in archaea?
No. Little to no mRNA capping, and splicing is not present since there are no introns.
