translation

Examples of translation in the following topics:

• Cancer and Translational Control

  • There are many examples of translational or post-translational modifications of proteins that arise in cancer.
  • Modifications are found in cancer cells from the increased translation of a protein to changes in protein phosphorylation to alternative splice variants of a protein.

• Prokaryotic versus Eukaryotic Gene Expression

  • To synthesize a protein, the processes of transcription (DNA to RNA) and translation (RNA to protein) occur almost simultaneously.
  • The newly-synthesized RNA is then transported out of the nucleus into the cytoplasm where ribosomes translate the RNA into protein.
  • The processes of transcription and translation are physically separated by the nuclear membrane; transcription occurs only within the nucleus, and translation occurs only outside the nucleus within the cytoplasm.
  • Regulation may occur when the DNA is uncoiled and loosened from nucleosomes to bind transcription factors (epigenetics), when the RNA is transcribed (transcriptional level), when the RNA is processed and exported to the cytoplasm after it is transcribed (post-transcriptional level), when the RNA is translated into protein (translational level), or after the protein has been made (post-translational level).
  • Further regulation may occur through post-translational modifications of proteins.

• The Initiation Complex and Translation Rate

  • The first step of translation is ribosome assembly, which requires initiation factors.
  • In translation, before protein synthesis can begin, ribosome assembly has to be completed.
  • Translation is ready to begin.
  • Therefore, the 43S complex cannot form properly and translation is impeded.
  • Discuss how eukaryotes assemble ribosomes on the mRNA to begin translation

• The Central Dogma: DNA Encodes RNA and RNA Encodes Protein

  • The reading frame for translation is set by the AUG start codon.
  • Translation is the process by which mRNA is decoded and translated to produce a polypeptide sequence, otherwise known as a protein.
  • Transfer RNA, or tRNA, translates the sequence of codons on the mRNA strand.
  • The genetic code for translating each nucleotide triplet (codon) in mRNA into an amino acid or a translation termination signal.
  • This interactive shows the process of DNA code being translated to a protein from start to finish!

• Cell Signaling and Gene Expression

  • To synthesize a protein, the processes of transcription and translation occur almost simultaneously.
  • The processes of transcription and translation are physically separated by the nuclear membrane: transcription occurs only within the nucleus, and translation occurs only outside the nucleus in the cytoplasm.
  • Regulation may occur when the DNA is uncoiled and loosened from nucleosomes to bind transcription factors (epigenetic level); when the RNA is transcribed (transcriptional level); when the RNA is processed and exported to the cytoplasm after it is transcribed (post-transcriptional level); when the RNA is translated into protein (translational level); or after the protein has been made (post-translational level).
  • Prokaryotic transcription and translation occur simultaneously in the cytoplasm; regulation occurs at the transcriptional level.
  • Further regulation may occur through post-translational modifications of proteins.

• The Process and Purpose of Gene Expression Regulation

  • Gene expression is a highly complex, regulated process that begins with DNA transcribed into RNA, which is then translated into protein.
  • For the proteins to be expressed, the DNA must be transcribed into RNA and the RNA must be translated into protein.
  • In a given cell type, not all genes encoded in the DNA are transcribed into RNA or translated into protein because specific cells in our body have specific functions.
  • At any given time, only a subset of all of the genes encoded by our DNA are expressed and translated into proteins.
  • In this section, you will learn about the various methods of gene regulation and the mechanisms used to control gene expression, such as: epigenetic, transcriptional, post-transcriptional, translational, and post-translational controls in eukaryotic gene expression, and transcriptional control in prokaryotic gene expression.

• The Mechanism of Protein Synthesis

  • When an in-frame AUG is encountered during translation elongation, a non-formylated methionine is inserted by a regular Met-tRNA.
  • Many, but not all, eukaryotic mRNAs are translated from the first AUG sequence.
  • The remaining eIFs dissociate from the ribosome and translation is ready to begins.
  • Termination of translation occurs when the ribosome moves over a stop codon (UAA, UAG, or UGA).
  • The ribosome A site is positioned over the second codon in the mRNA reading frame, and translation elongation can begin.

• Altered Gene Expression in Cancer

  • This can be the result of gene mutation or changes in gene regulation (epigenetic, transcription, post-transcription, translation, or post-translation).
  • Changes in epigenetic regulation, transcription, RNA stability, protein translation, and post-translational control can be detected in cancer.
  • Therefore, changes in histone acetylation (epigenetic modification that leads to gene silencing), activation of transcription factors by phosphorylation, increased RNA stability, increased translational control, and protein modification can all be detected at some point in various cancer cells.
  • Overexpression of the oncogene can lead to uncontrolled cell growth because oncogenes can alter transcriptional activity, stability, or protein translation of another gene that directly or indirectly controls cell growth.

• The Relationship Between Genes and Proteins

  • Since the rediscovery of Mendel's work in 1900, the definition of the gene has progressed from an abstract unit of heredity to a tangible molecular entity capable of replication, transcription, translation, and mutation.
  • Replication, Transcription, and Translation are the three main processes used by all cells to maintain their genetic information and to convert the genetic information encoded in DNA into gene products, which are either RNAs or proteins, depending on the gene.
  • In eukaryotic cells, or those cells that have a nucleus, replication and transcription take place within the nucleus while translation takes place outside of the nucleus in cytoplasm.
  • Translation makes protein from mRNA.

• Regulating Protein Activity and Longevity

  • These changes can alter protein function, epigenetic accessibility, transcription, mRNA stability, or translation; all resulting in changes in expression of various genes.
  • Because proteins are involved in every stage of gene regulation, the phosphorylation of a protein (depending on the protein that is modified) can alter accessibility to the chromosome, can alter translation (by altering transcription factor binding or function), can change nuclear shuttling (by influencing modifications to the nuclear pore complex), can alter RNA stability (by binding or not binding to the RNA to regulate its stability), can modify translation (increase or decrease), or can change post-translational modifications (add or remove phosphates or other chemical modifications).
  • Methyl groups are added to proteins via the process of methylation; this is the most common form of post-translational modification.