Characterizing Unique Protein: DNA Interactions Using Cell-Free Protein Expression

Molecular model of human telomere DNA
Molecular model of human telomere DNA

The POT1 protein plays a critical role in telomere protection and telomerase regulation. POT1 binds single-stranded 5′-TTAGGGTTAG-3′ and forms a dimer with the TPP1 protein. Human POT1 contains two Oligonucleotide/Oligosaccharide Binding (OB) fold domains, OB1 and OB2, which make physical contact with the DNA. OB1 recognizes 5′-TTAGGG whereas OB2 binds to the downstream TTAG-3′ (1,2). Several recent studies from other species have shown that some of these proteins are able to recognize a broader variety of DNA ligands than expected (3). A recent reference reexamined the sequence-specificity of the Human POT1 protein (4).
SELEX (Systematic Evolution of Ligands through Exponential Enrichment) was used  to re-examine the DNA-binding specificity of human POT1 (5). Continue reading “Characterizing Unique Protein: DNA Interactions Using Cell-Free Protein Expression”

Why Stress is Bad for Your Cells

ostrichThere are some things that science can tell me that I’m not sure I want to know. For example, I’m not sure I want to know the sequence of my own genome and my projected risk of developing any particular, currently incurable diseases. There are some things it is better not to know, particularly if there is nothing you can do about it anyway. Until recently I would have put telomere length into this category as well. Short telomeres are an indicator of biological age and are associated with increased susceptibility to diseases of aging. And stress, such as could be caused by worrying about how short your telomeres are, is known to make them even shorter. So why find out? It turns out that there are some things under our control that can positively affect telomere length.

Telomeres are nucleoprotein structures at the end of chromosomes that protect them from damage and ensure that genetic information is not lost during cell division. DNA polymerases cannot replicate DNA at the ends of chromosomes effectively, and without the protective effects of telomeres a small amount of chromosomal DNA would be lost with each cycle of cell division. The stretches of repetitive telomere DNA prevent progressive shortening of the chromosome, but are themselves shortened with each cell division. Telomere shortening limits the number of times that a cell can divide. Somatic cells are capable of a finite number of divisions, a number known as the Hayflick limit. Once cells reach that limit, they die. This limit is associated with telomere length. Once telomeres reach a critical length, cellular senescence is triggered, and a cell stops dividing and dies. Because of this, telomere length can act as a gauge of cellular or “biological” age. Continue reading “Why Stress is Bad for Your Cells”