Este documento describe los mecanismos de regulación de la expresión génica en organismos eucariotas. La expresión génica está regulada a través de modificaciones en la cromatina, procesamiento del RNA, iniciación de la traducción y procesamiento de proteínas. Factores como la acetilación de histonas, metilación del DNA y procesamiento alternativo del RNA influyen en la expresión de genes específicos en diferentes tipos celulares.
4. Figure 18.6 Signal
NUCLEUS
Chromatin
Chromatin modification:
DNA unpacking involving
histone acetylation and
DNA demethylation
DNA
Gene available
for transcription
Gene
Transcription
RNA Exon
Primary transcript
Intron
RNA processing
Tail
Cap mRNA in nucleus
Transport to cytoplasm
CYTOPLASM
mRNA in cytoplasm
Degradation Translation
of mRNA
Polypeptide
Protein processing, such
as cleavage and
chemical modification
Active protein
Degradation
of protein
Transport to cellular
destination
Cellular function (such
as enzymatic activity,
structural support)
5. Figure 18.6a
Signal
NUCLEUS
Chromatin
Chromatin modification:
DNA unpacking involving
histone acetylation and
DNA demethylation
DNA
Gene available
for transcription
Gene
Transcription
RNA Exon
Primary transcript
Intron
RNA processing
Tail
Cap mRNA in nucleus
Transport to cytoplasm
CYTOPLASM
6. Figure 18.6b
CYTOPLASM
mRNA in cytoplasm
Degradation Translation
of mRNA
Polypeptide
Protein processing, such
as cleavage and
chemical modification
Active protein
Degradation
of protein
Transport to cellular
destination
Cellular function (such
as enzymatic activity,
structural support)
15. Figure 18.8-3
Enhancer Proximal Poly-A
(distal control control Transcription signal Transcription
elements) elements start site sequence termination
region
DNA Exon Intron Exon Intron Exon
Upstream Downstream
Promoter Transcription Poly-A
signal
Primary RNA Exon Intron Exon Intron Exon Cleaved
transcript 5ʹ′ 3ʹ′ end of
(pre-mRNA) primary
RNA processing
transcript
Intron RNA
Coding segment
mRNA G P P P AAA ⋅⋅⋅ AAA 3ʹ′
Start Stop
5ʹ′ Cap 5ʹ′ UTR codon codon 3ʹ′ UTR Poly-A
tail
UTR untranslated region
21. Figure 18.10-3
Activators Promoter
Gene
DNA
Distal control
Enhancer element TATA box
General
transcription
factors
DNA-
bending
protein
Group of mediator proteins
RNA
polymerase II
RNA
polymerase II
Transcription
initiation complex RNA synthesis
22. Control combinatorial de la activación génica
• Una combinación particular de elementos de
control puede activar la transcripción sólo cuando
las proteínas activadoras apropiadas están
presentes.
23. Figure 18.11 Enhancer Promoter
Control
elements Albumin gene
Crystallin
gene
LIVER CELL LENS CELL
NUCLEUS NUCLEUS
Available Available
activators activators
Albumin gene
not expressed
Albumin gene
expressed
Crystallin gene
not expressed
Crystallin gene
expressed
(a) Liver cell (b) Lens cell
24. Figure 18.11a
Enhancer Promoter
Control LIVER CELL
elements Albumin gene NUCLEUS
Available
Crystallin activators
gene
Albumin gene
expressed
Crystallin gene
not expressed
(a) Liver cell
25. Figure 18.11b
Enhancer Promoter
Control LENS CELL
elements Albumin gene NUCLEUS
Available
Crystallin activators
gene
Albumin gene
not expressed
Crystallin gene
expressed
(b) Lens cell
37. Figure 18.14
Proteasome
Ubiquitin and ubiquitin
to be recycled
Proteasome
Protein to Ubiquitinated Protein
be degraded protein fragments
Protein entering (peptides)
a proteasome
La ubiquitina es una pequeña proteína reguladora que ha sido
encontrada en la mayoría de los tejidos de los organismos
eucariotas. Una de sus muchas funciones es dirigir el reciclaje de
proteínas (wikipedia 2013).
40. Figure 18.15
Hairpin
miRNA Hydrogen
bond
Dicer
5ʹ′ 3ʹ′
(a) Primary miRNA transcript miRNA miRNA-
protein
complex
Hairpin=Horquillas son un
tipo común de estructura
secundaria en moléculas
de ARN.
http://www.nature.com/scitable/definition/hairpin-
loop-mrna-314
mRNA degraded Translation blocked
(b) Generation and function of miRNAs