Gene Anatomy

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Concencus Sequences of Eukaryotic Organisms
Fatih Mehmet IPEK Biology 4 01040011
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DNA tamplate carries 2 major concensus sequences
present on upstream of -35 and -10bp position.
DNA dependent RNA polymerase enzymes (r)
subunit is able to recognise these cencensus
sequenes.
-35 bp position is composed of TTGACA -10 bp is
composed of TATAATAAT (that part is known TATA
box).
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DNA tamplate also carries inverted repeats which
is composed of G-C and A-T rich sequences. The
resion behind of this is termination of the
transcribtion procedure.
For instance 5 ACT-GGCTCC-AAAA-GGAGCC-AAAAAA
3 DNA tamplate
G-C rich G-C rich A-T rich
U U U U
mRNA
H bonds
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Eukaryotic mRNA Eukaryotic mRNA is
monocistronic sequences. Eukaryotic mRNA needs
maturation in order to pass the cytoplasm from
the nucleus. And maturation involves in 3 steps

• CAP protein must be edded to the 5 end.
• PolyA tail ought to add to the 3 end of the
  mRNA.
• This polyA tail composed of 50 to 250bp lenght
  of Adenin base repeats. PolyA polymerase enzyme
  synthesises that part. This enzyme recognise
  AAUAAA sequence on the 3 of mRNA and it will
  remove bases downstream on the mRNA. Then it adds
  50-250 bp of Adenin bases.

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3. Eukaryotic mRNA consists of intronic and
exonic sequences. Splicing of intron is applied
with spliciosome enzyme which is
ribonucleoprotein complex (small nuclear RNA
proteins). This enzyme can recognise introns by
certain sequences.
5 (A/C)AGGU(A/G)AUG(6 Pyrimidin)CAGG(G/U)
..3 mRNA
EXON
INTRON EXON
5UTR 3UTR
mRNA
exon 1 intron exon 2
intron exon 3
Exon 1 Exon 2 Exon 3
5UTR 3UTR
mRNA
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5 3 UnTranslated Regions (UTR) The crucial
role of the non-coding portion of genomes is now
widely acknowledged. In particular, mRNA
untranslated regions are involved in many
post-transcriptional regulatory pathways.
The nontranslated 5end (leader) is relatively
short, usually (but not always) less than 100bp.
The length of the nontranslated 3end (trailer)
is often rather longer, sometimes around 1000bp.
5-UTR sequences were defined as the mRNA region
spanning from the cap site to the starting codon
(excluded), whereas 3-UTR sequences were defined
as the mRNA region spanning from the stop codon
(excluded) to poly(A) starting site.
 
mRNA
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5 3 UnTranslated Regions of eukariotic mRNAs
are known to play a crucial role in

• The 5-and 3-UTR Post-transcriptional regulation
  of gene expression modulating nucleo-cytoplasmic
  mRNA transport.
• Control of mRNA cellular and subcellular
  localization.
• Control of mRNA stability.
• Control of mRNA translation efficency.

Several regulatory signals have already been
identified in 5-and 3-UTR sequences, usually
corresponding to short oligonucleotide tracts,
also able to fold in specific secondary
structures, which are protein binding sites for
various regulatory protein.
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•  REFERENCES   
• Lewin B, Genes 6.addition
• Pesole G, Grillo G, Liuni S, Licciulli F, Mignone
  F, Gissi G, Saccone C. UTRdb and UTR
  sitespecialized databases of sequences and
  functional elements of 5and 3untranslated
  regions of eukariotic mRNAs. Update 2002.
  
• Meijer H.A, Thomas A.M control of eukaryotic
  protein synthesis by open reading frames in
  5-untranslated region of an mRNA.
• Pesole G, Grillo G, Larizza A, Liuni S The
  untranslated regions of eukaryotic mRNAs
  structure, function, evolution and bioinformatic
  tools for their analysis.