زیست شناسی سلولی و مولکولی (Cellular and Molecular Biology) بخش مهندسی بیوتکنولوژی عنوان درس: زیست شناسی سلولی و مولکولی (Cellular and Molecular Biology) تعداد واحد: 2 (نظری) روش ارزیابی: 15% سمینار، 35% میان ترم و 50% پایان ترم

Regulation of Gene Expression Lecture 3 Regulation of Gene Expression

Recently it has become clear that only a small percentage (7%) of disease-associated single nucleotide polymorphisms (SNPs) are located in protein-coding regions, while the remaining 93% are located in gene regulatory regions or in intergenic regions.

Level of Regulation of Gene Expression Chromatin structure Initiation of transcription Processing of the transcript Transport to the cytoplasm Translation of mRNA mRNA stability Protein activity stability.

Control of Gene Expression in Bacteria In bacteria, the genes that encode the enzymes of a metabolic pathway are usually clustered together on the chromosome in a functional complex called an operon.

Sigma Factors Sigma factors are multi-domain subunits of bacterial RNA polymerase (RNAP) that play critical roles in transcription initiation, including the recognition and opening of promoters as well as the initial steps in RNA synthesis

The lac operon

The trp operon In a repressible operon, such as the tryptophan (or trp) operon, the repressor is unable to bind to the operator DNA by itself. Instead

Many Bacterial Responses Are Controlled by Two-Component Regulatory Systems

Three-dimensional structures of bacterial and eukaryotic RNA polymerases. This heptapeptide repeat, with a consensus sequence of Tyr-Ser-Pro-Thr-Ser-Pro-Ser, is known as the carboxyl-terminal domain (CTD)

Structure of the 5 methylated cap of eukaryotic mRNA The cap protects an mRNA from enzymatic degradation and assists in its export to the cytoplasm. The cap also is bound by a protein factor required to begin translation in the cytoplasm

Transcription from a particular promoter is controlled by DNA- binding proteins, termed transcription factors, that are equivalent to bacterial repressors and activators.a

Regulatory Sequences in Protein-Coding Genes TATA Box Initiators CpG Islands (5) Y-Y-A1-N-T/A-Y-Y-Y (3) Most genes of this type contain a CG-rich stretch of 20–50 nucleotides within ≈100 base pairs upstream of the start-site region.

Promoter-Proximal Elements control regions lying within 100–200 base pairs upstream of the start site. Enhancers: long-distance transcription-control elements (>200 bp)

Activators and Repressors of Transcription DNase I footprinting Electrophoretic mobility shift assay Sequence specific DNA affinity chromatography

DNase I footprinting

Electrophoretic mobility shift assay

Sequence specific DNA affinity chromatography