Due to the unified mode of inactivation of the pRb/p16 pathway and existence of the regulatory feedback the vast majority of HR-HPV-positive cervical tumors display strong a p16ink4a expression.
Since viruses have mechanisms to block type I IFN expression and intracellular signaling pathways, the existence of other mechanisms regulating typical IFN-responsive genes is critical to anti-viral responses.
Our studies also showed a pattern of intermixing between the color and disparity pathways of V2, including the existence of single cells tuned for both color and disparity.
Also, it was recently elucidated that HIF-1 α protein synthesis depends on a phosphatidylinositol 3-kinase (PI3 K-) Akt-mammalian target of the rapamycin (mTOR) signaling transduction pathway because of the existence of a polypyrimidine tract in the 5′-untranslated region of HIF-1 α mRNA [ 31, 32].
The analysis of the model for this pathway identified existence of two different dynamical regimes, and depending on parameters, the system can switch from single-state bi-stability to oscillations [ 63].
However, although there is evidence to suggest that glyphosate can inhibit multiple cellular functions such as mitochondrial respiration, and enzyme activities other than EPSPS within the shikimate pathway, the existence of such direct mechanisms of interference at the low environmental dose tested here currently remains unknown and thus needs further exploration.
The major distinctions of Sc. pombe cells in the control of lesion tolerance pathways are the existence of pathways that involve various TLS polymerases, the TLS requirement for enzymes needed for mono- and polyubiquitination of PCNA and, surprisingly, the mostly error-free bypass of various DNA lesions regardless of the polymerase or polymerases synthesizing through them (Coulon et al. 2010).
The requirement of Src and Mek, but not PI3K, for MN survival by Met2S implies either a parallel action of Src and Mek-ERKs pathways, or the existence of a circuit involving activation of Mek-ERKs by Src.
Even in organisms with the complete biosynthetic pathway, the existence of B12 and precursor transporters may impart selective advantages during times of hardship or during different life stages.
Caveolin is the major component of another very well described endocytic pathway, the so-called caveolae-dependent endocytic pathway, the existence of which in B-cells is controversially [53], [54], [55], [56], [57].
