BIOL 321 - Translational Regulation Flashcards

Vocabulary flashcards covering eukaryotic translational regulation, mRNA structural elements, embryonic translational control, iron homeostasis regulation, and post-translational protein processing.

Heteronuclear RNA (hnRNA)

The primary RNA transcript ($1^\text{o}$ transcript) synthesized in the nucleus prior to processing into mature mRNA.

Differential Splicing

The selective splicing of a primary transcript that produces alternate mRNA transcripts encoding completely different proteins, influenced by $\text{U-snRNP}$ components and cell-specific proteins.

Cytoplasmic Polyadenylation Element (CPE)

A specific sequence motif ($\text{UUUAU}$) in the $3'\text{UTR}$ of mRNA that marks stored maternal mRNAs for selective polyadenylation upon fertilization.

Maskin

An interfering protein recruited by CPEB on stored embryonic mRNAs that binds to $\text{eIF4E}$ and blocks polyadenylation and translation initiation until CPEB is phosphorylated.

CPEB (CPE Binding Protein)

A protein that binds to the Cytoplasmic Polyadenylation Element in the $3'\text{UTR}$ of mRNA and recruits Maskin to keep the mRNA translationally dormant.

PUF Family Proteins

A family of proteins, such as Pumilio in Drosophila, that bind to specific elements in the $3'\text{UTR}$ of mRNA to prevent polyadenylation and inhibit translation.

Masked Messages

mRNAs packaged into ribonucleoprotein (RNP) particles in unfertilized eggs, which prevent ribosome attachment until ionic changes ($\text{Ca}^{2+}$, $\text{Na}^+$, pH) at fertilization release the masking proteins.

Internal Ribosomal Entry Site (IRES)

A structural sequence motif within mRNA that allows for cap-independent translation initiation, commonly used by viral mRNAs and certain human anti-apoptotic mRNAs.

Bicoid Protein

A protein synthesized at the anterior pole of a Drosophila egg that forms a gradient, functioning as a transcription factor and a translational repressor of Caudal mRNA.

4EHP

An interfering protein recruited by Bicoid bound to the $3'\text{UTR}$ of Caudal mRNA that binds the $m^7\text{G}$ cap and prevents translation initiation complex assembly.

Ferritin

An intracellular iron storage protein whose mRNA translation is blocked when iron levels are low, and stimulated when iron levels are high to safely store excess iron.

Transferrin Receptor

An iron transport cell-surface protein whose mRNA is stabilized under low iron conditions to increase protein synthesis, and degraded under high iron conditions.

Iron-Responsive Element (IRE)

A hairpin RNA structure located in the $5'\text{UTR}$ or $3'\text{UTR}$ of mRNAs encoding iron-metabolism proteins that binds Iron Regulatory Proteins (IRPs).

Iron Regulatory Proteins (IRPs)

Trans-acting proteins (IRP-1 and IRP-2) that bind to IREs on mRNA; direct binding of iron to IRPs inactivates their ability to bind IREs.

Proprotein Convertase

An enzyme that carries out post-translational processing by proteolytically cleaving precursor proteins into active, mature proteins.

Proopiomelanocortin (POMC)

A precursor polypeptide encoded by the POMC gene that undergoes tissue-specific proteolytic cleavage by convertases to generate distinct bio-active peptides like ACTH, \text{\beta-Lipotropin}, \text{\textalpha-MSH}, and \text{\beta-Endorphin}.