Regulation of Gene Expression – Part II Spring 2013 - Althoff Reference: Mader & Windelspecht Ch. 13) Lec 19 • Eukaryotic Regulation

Eukaryotic Regulation With few known exceptions….____________ of a multicellular eukaryote has a complete complement of genes. Cell type differences (i.e., muscle vs. nerve vs. liver vs. etc.) result because only a certain set of genes is “___________” in the ___________…thus, a different set of proteins are “active” in the cytoplasm. There are 5 primary levels of control: 3 pertain to the __________, 2 of them pertain to the _____________

Eukaryotic Regulation – 5 types of control 1 Chromatin Structure – in the nucleus Transcriptional Control – in the nucleus Posttranscriptional Control – in the nucleus Translational Control — in the cytoplasma Posttranslational Control – in the cytoplasma 2 3 4 5

1 Nucleus 2 3 Cytoplasma 4 5

Type: Chromatin Structure 1 Chromatin packing is used as a way to keep genes turned ____. If genes are not accessible to ________________, they cannot be ___________. Chromatin structure is one method of __________ ___________ = transmission of genetic information “__________” the ______________ of a gene. Chromatin is a “stringy” variety of proteins material… most prevalent during interphase of the cell cycle

Type: Chromatin Structure 1 One class of DNA-associated proteins are ____________. They play an important role in ________________ of DNA. Without histones, DNA could not fit inside the nucleus. Each human cell contains about 2 meters of DNA…yet the nucleus is only 5-8 цm in diameter. _______________ chromatin = ______________

Nucleus with staining showing… heterochromatin and euchromatin nucleolus

nucleosome DNA Unpacking _____________ promoter chromatin remodeling 1 chromatin remodeling ___________ promoter 2 3 DNA to be __________

Type: Chromatin Structure 1 Heterochromatin is not transcribed… Heterochromatin does not permit access by RNA polymerase Genes contained by heterochromatin __________ _______ get transcribed…therefore they are not expressed Example: Barr body in mammalian females (XX): chromatin adheres to inner edge of the nuclear membrane—resulting in one inactive X chromosome (i.e., produces no products)

Type: Chromatin Structure 1 __________ Inheritance: sometimes caused by histone modification…changes that result not in sequence of DNA nucleotides. Epigenetic inheritance term is not restricted to the genes themselves causing variation. Epigenetic inheritance may explain unusual patterns of inheritance …and may play a role in growth, aging, and cancer.

Type: Transcriptional Control 2 This is considered the _____________ of the 5 control levels Keep in mind that the first step towards transcript is availability of DNA A eukaryote may have many different types of _________________—proteins that help regulate transcription by assisting RNA polymerase to bind to the _______________. There may be __________________ transcription factor active at a single promoter…thus, the absence of one can prevent transcription from taking place

Type: Transcriptional Control 2 Even with all transcription factors present, transcription might not begin without the presence of a DNA-binding protein called a _____________ ______________ Transcription activators bind to regions of the DNA called _______________. Enhancers may not be located near promoters… “Distance” reduced with _____________ in the DNA

_________________________ 1 enhancer 2 transcription activator 3 _________________________

Type: Posttranscriptional Control Occurs in the nucleus Includes alternative mRNA splicing and controlling of the _____ with which mRNA leaves the nucleus During pre-mRNA splicing, ________ (non-coding regions) are excised…and ________ (expressed regions) are joined together to form an mRNA. Result: if an exon is _________, it may be is excised along with flanking introns…the result… ….the ___________ has an altered sequence and the protein it encoded is altered Example: in thyroid, a slightly different calcitonin than what the hypothalamus produces. 3

what happens in the nucleus in the cytoplasma what happens Protein product 1 Protein product 2

Type: Translational Control Occurs in the cytoplasma Happens __________ a protein product is made Associated with activity of the mRNA for translation at the ______________ Affected by the presence…or…absence… of the 5’ cap and the length of the poly-A (i.e., adenine nucleotide) tail at the 3’ end…this can affect the whether a) __________________…or for _____ _____ the mRNA is active. Example: persistence 5’ end caps and long 3’ poly-A tails long-life of mRNAs that code for hemoglobin in mammalian red blood cells 4

Type: Posttranslational Control Occurs in the cytoplasma Begins once the __________________________ and become active. It represents the last chance the cell has for influencing gene expression This highlights the fact that not all proteins are “active” after synthesis. Value of this: a protein is only activated when it is appropriate to do so. Example: bovine proinsulin is “held” as such before special bonding process that results in “active” insulin. 5

Type: Posttranslational Control Length of time a protein remains active in a cell usually regulated by ____________ = enzymes that breakdown proteins. Proteases usually confined to ____________ or special structures called _________________. 5

Type: Posttranslational Control For a protein to enter a proteasome, it has to be “tagged” with a signaling protein recognized by the proteasome’s cap. When the cap recognizes the tag, it opens up and allows the protein to enter the core of the structure where it is ___________________________. This is gene expresssion control” because it regulates the amount of protein product in the cytoplasma 5

Posttranslational Control: “________” 5 Which leads to ________ into proteasome where…

Posttranslational Control: “___________” 5 …break down to _______________________.

modification of DNA via In summary…. modification of DNA via chromatin structure transcriptional posttranscriptional translational posttranslational transcription translation mRNA protein DNA