RNA polymerases I/II/III
转录是一个very low-efficient的过程
转录速度：1min/2kb
super-enhancer，调控细胞命运与状态的重要元件
TF in reprogramming
Splicing
mRNA splicing is wide-spread in eukaryotes
Group I intron can be used as a biotech tool to synthesize circular RNA
RNA环化方法，可以防止RNA被降解，提高RNA的稳定性
spliceosome and splicing
催化的活性中心是RNA, U1, U2, U4, U5 snRNA
the discovery of snRNPs
three types of spliceosome
- major
- U12-type
- trans
Introns in human genes
fraction of intron sequences > 70%
aberrant forms of splicing
- exon skipping
- cryptic splicing
- intron retention
基因越长，发生错误的概率越高
大约90% human genes undergo alternative splicing
alternative splicing is regulated by combinations of cis-elements and trans-factors
数量：
- TF 2k-3k
- RNA binding protein 2k-3k
- splicing factor 200-300
可变剪接可以导致一个基因能够产生约4万种蛋白
Mutually exclusive splicing of multiple exons
Splicing can generate circular RNAs
splicing and regulation of stem cells
splicing and metabolism in cancer
splicing and disease, 剪接和疾病非常相关
Spinal Muscular Atrophy 骨髓性肌肉萎缩症
SMN1 出问题。是SMN complex的重要组分
治疗错误splicing的SMN2
除了靶向splicing factor，还可以直接靶向RNA
Why introns exist?
Big introns > 100kb, how are they removed?
How are small exons and introns spliced?
RNA polyadenylation and Gene regulation
Replication dependent histone mRNAs are only mRNA without poly A tail in metazoan
polyA in mammalian mitochondria: stabilizing or destabilizing mRNA?
High-throughput sequencing to determine polyA length
Alternative polydenylation determines 3’ UTR or protein products
APA widely exists in eukaryotes
shortening of 3’-UTR correlates with tumorigenesis
determine subtypes of stem cell
近端的polyA位点通常是weak factor，远端通常是strong factor