Gene Expression Shred Fest II LO Flashcards
what is a nucleosome?
octamer of 8 histone proteins with DNA wrapped around it
2 of each (H2A, H2B, H3, and H4)
how many base pairs of DNA wrap around a histone?
147 bp
which is negative and which is positive between DNA and histones?
DNA negative, histone positive
what are the 2 forms of chromatin?
heterochromatin
euchromatin
what is heterochromatin?
highly condensed chromatin that is transcriptionally inactive and sterically inaccessible
what is euchromatin?
less condensed, transcripationally active, sterically accessible
what are the 2 classes of chromatin remodeling factors?
DNA dependent ATPases
HATs and HDACs
what is an example of a DNA-dependent ATPase?
SWI/SNF
what is the function of SWI and SNF?
disrupt histone octamers and DNA to allow for previously unaccesible areas of DNA to be accessed through ATP hydrolysis
what is the function of HATs and HDACs?
reversibly modify histones through acetylation
what is a HATs?
histone acetyltransferases
what is a HDACs?
histone deacetylases
what is the specific function of HATs?
acetylate N-termini of histones thus causing neutralization of histone and releasing DNA from histone
what is the specific function of HDACs?
histones retain their positive charge
what is the histone code hypothesis?
lysine acetylation on histones thought to generate binding sites for protein-protein interactions which helps recruit different domains that alter chromatin structure allowing pol access to DNA
what is the function of CREB binding protein (CBP)?
transcriptional coactivator for many different transcription factors, regulates cell growth and division and required for normal fetal development
what is the cause of Reubinstein-Taybi Syndrome?
mutations in one copy of CREB binding protein, causes haploinsufficiency and results in widespread transcriptional changes due to lack of activation of transcription
how is leukemia caused with regards to HATs and HDACs?
it is a hematopoietic malignancy, generally result of chromosomal translocations leading to gain of function fusion proteins, causes fusion of HATs and HDACs and alters the activity of these regulators
what is haploinsufficiency?
person has only one functional copy of a gene and that one gene does not produce enough protein to allow for wild type phenotype
what do transcriptional activators recruit to change chromatin?
HATs, activate transcription
what do transcriptional repressors recruti to change chromatin?
HDAC, deactivate transcription
what are specificity factors?
factors that alter the affinity of RNA polymerase and thus increase or decrease transcription levels
how do repressors affect transcription?
they bind to non-coding sequences on DNA strand close to the promoter region, impedes RNA pol progress on strand
how do activators affect the level of transcription?
increase attraction of RNA pol to promoter through interactions with pol directly or with structure of DNA
how do enhancers affect the level of transcription?
bind to sites on DNA helix that are bound by activators to loop the DNA and bring a specific promoter to the initiation complex
