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Related Concept Videos

Pre-mRNA Processing: Modification of pre-mRNA Ends01:35

Pre-mRNA Processing: Modification of pre-mRNA Ends

In eukaryotic cells, transcripts made by RNA polymerase are modified and processed before exiting the nucleus. Unprocessed RNA is called precursor mRNA or pre-mRNA to distinguish it from mature mRNA.
Once about 20-40 ribonucleotides have been joined together by RNA polymerase, a group of enzymes adds a cap to the 5' end of the growing transcript. In this process, a 5' phosphate is replaced by modified guanosine that has a methyl group attached (7-methyl guanosine). This 5' cap helps the cell...
Nonsense-mediated mRNA Decay02:27

Nonsense-mediated mRNA Decay

The Upf proteins that carry out nonsense-mediated decay (NMD) are found in all eukaryotic organisms, including humans. Each protein has an individual role, but they need to work in collaboration. Upf1 is an ATP-dependent RNA helicase that unwinds the RNA helix. Because Upf1 can unwind any RNA, Upf2 and Upf3 are required to help Upf1 discriminate between nonsense and normal mRNAs.
Usually, Upf3 binds to an Exon Junction Complex (EJC) at mRNA splice sites. If a ribosome fully translates the mRNA,...
Nonsense-mediated mRNA Decay02:27

Nonsense-mediated mRNA Decay

The Upf proteins that carry out nonsense-mediated decay (NMD) are found in all eukaryotic organisms, including humans. Each protein has an individual role, but they need to work in collaboration. Upf1 is an ATP-dependent RNA helicase that unwinds the RNA helix. Because Upf1 can unwind any RNA, Upf2 and Upf3 are required to help Upf1 discriminate between nonsense and normal mRNAs.
Usually, Upf3 binds to an Exon Junction Complex (EJC) at mRNA splice sites. If a ribosome fully translates the mRNA,...
Tail-anchoring of Proteins in the ER Membrane01:45

Tail-anchoring of Proteins in the ER Membrane

Tail-anchored, or TA, proteins are estimated to make up to 3-5% of membrane proteins found in the eukaryotic cell. Such proteins have a single transmembrane domain located approximately 30 amino acid residues upstream from the C-terminal end. As a result, the signal recognition particle (SRP) cannot guide a TA protein to the ER membrane for cotranslational insertion. Hence, they are integrated into the ER membrane post-translationally using their C-terminal end as the anchor. TA proteins...
Export of Misfolded Proteins out of the ER01:32

Export of Misfolded Proteins out of the ER

After folding, the ER assesses the quality of secretory and membrane proteins. The correctly folded proteins are cleared by the calnexin cycle for transport to their final destination, while misfolded proteins are held back in the ER lumen. The ER chaperones attempt to unfold and refold the misfolded proteins but sometimes fail to achieve the correct native conformation. Such terminally misfolded proteins are then exported to the cytosol by ER-associated degradation or ERAD pathway for...
Other Glycolytic Pathways01:24

Other Glycolytic Pathways

The pentose phosphate pathway (PPP) operates in parallel with glycolysis, facilitating the metabolism of both pentoses and glucose. This pathway consists of two distinct phases: the oxidative and non-oxidative phases. While it does not directly generate ATP, the intermediates formed during the process can integrate into glycolysis, contributing to cellular energy metabolism when required.Oxidative Phase: NADPH ProductionThe oxidative phase of the pentose phosphate pathway is primarily...

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Related Experiment Video

Updated: May 23, 2026

Functional Complementation Analysis (FCA): A Laboratory Exercise Designed and Implemented to Supplement the Teaching of Biochemical Pathways
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Functional Complementation Analysis (FCA): A Laboratory Exercise Designed and Implemented to Supplement the Teaching of Biochemical Pathways

Published on: June 24, 2016

The N-end rule pathway.

Takafumi Tasaki1, Shashikanth M Sriram, Kyong Soo Park

  • 1Center for Pharmacogenetics and Department of Pharmaceutical Sciences, School of Pharmacy, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, USA.

Annual Review of Biochemistry
|April 25, 2012
PubMed
Summary

The N-end rule pathway identifies protein degradation targets using N-terminal residues. This essential system regulates cellular processes and interacts with small molecules.

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Cell Biology

Background:

  • The N-end rule pathway is a conserved proteolytic system.
  • It recognizes N-terminal residues of proteins to target them for degradation.
  • This pathway involves N-recognins, N-degrons, and the 26S proteasome.

Purpose of the Study:

  • To review the biochemical mechanisms, structures, and physiological functions of the N-end rule pathway.
  • To explore the regulation of the N-end rule pathway by small molecules.

Main Methods:

  • Literature review of existing research on the N-end rule pathway.
  • Analysis of biochemical mechanisms, protein structures, and physiological roles.
  • Examination of small molecule interactions and regulatory roles.

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Analysis of RNA Processing Reactions Using Cell Free Systems: 3' End Cleavage of Pre-mRNA Substrates in vitro
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Analysis of RNA Processing Reactions Using Cell Free Systems: 3' End Cleavage of Pre-mRNA Substrates in vitro

Published on: May 3, 2014

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Last Updated: May 23, 2026

Functional Complementation Analysis (FCA): A Laboratory Exercise Designed and Implemented to Supplement the Teaching of Biochemical Pathways
09:27

Functional Complementation Analysis (FCA): A Laboratory Exercise Designed and Implemented to Supplement the Teaching of Biochemical Pathways

Published on: June 24, 2016

A Web Tool for Generating High Quality Machine-readable Biological Pathways
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A Web Tool for Generating High Quality Machine-readable Biological Pathways

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Analysis of RNA Processing Reactions Using Cell Free Systems: 3' End Cleavage of Pre-mRNA Substrates in vitro
09:16

Analysis of RNA Processing Reactions Using Cell Free Systems: 3' End Cleavage of Pre-mRNA Substrates in vitro

Published on: May 3, 2014

Main Results:

  • N-terminal residues act as signals for protein degradation via N-degrons.
  • N-recognins mediate ubiquitylation and proteasomal degradation.
  • N-degrons can be generated by proteolytic cleavage or post-translational modifications.
  • The pathway is conserved across eukaryotes and prokaryotes.
  • Small molecules modulate the N-end rule pathway's function in homeostasis.

Conclusions:

  • The N-end rule pathway is a fundamental proteolytic mechanism crucial for cellular homeostasis.
  • Understanding its mechanisms and regulation by small molecules offers insights into physiological processes.