Cellular Homology

Some Retroviral Oncogenes and Their Cellular Homologs ... 

Oncogene Viral Origin j Viral Gene Product 1 Cellular Homolog Activity Subcellular Location... 

The c-myc gene, identified originally as the cellular homolog of the transforming determinant carried by avian myelocytomatosis virus, is altered in association with a broad spectrum of neoplasms. Consistent with the observation that altered c-myc is associated with tumors of diverse origin, it has been observed that normal c-myc is expressed in a variety of tissues. Thus, c-myc appears to encode a function associated with a ubiquitous metabolic pathway. 

Knappe, A., Hor, S., Wittmann, S., and Fickenscher, H. (2000). Induction of a novel cellular homolog of interleukin-10, AK155, by transformation of T lymphocytes with herpesvirus saimiri./. Virol. 74, 3881-3887. 

Cellular Bcl-2 and Bc1-xl have a hydrophobic membrane-interacting domain at their C-terminus and are found mainly in mitochondria and in the endoplasmic reticulum. Bcl-2 and Bc1-Xl prevent the release of mitochondrial cytochrome c and subsequent activation of caspases (Kluck et al. 1997), presumably by interacting with mitochondrial membrane channels like VDAC and adenine nucleotide translocator (Shimizu et al. 1999). Very similar to its cellular homologs, the //. 6f/m/r/-encoded Bcl-2 stabilizes mitochondria and inhibits the activation of caspase-3 (Derfuss et al. 1998). 

Phosphatase tensin on chromosome ten mutated in multiple advanced cancers Phosphatidyl inositol kinase cellular homolog AKT 8 mouse thymic retroviral oncogene PDZ postsynaptic density protein drosophila disc large tumor suppressor ZO zonula occludens... 

Simplicial computations, even for such small spaces as the torus, can be rather tedious. A quicker way to compute is provided by the cellular homology, which we introduce in Section 3.6. 

The winding number of a closed curve, and more generally, the degree of a continuous map between spheres of the same dimension, are invariants, which are useful in many situations. We shall need these to define the so-called incidence numbers, which in turn allow one to give an explicit description of cellular homology. 

Definition 3.38. For an arbitrary CW complex A, the homology groups of the cellular chain complex defined above are called cellular homology groups of A, and are denoted by iJ "(Z 7 .). 

It is important to note that the cellular homology also enjoys functoriality as long as the maps are taken to be cellular. 

Again we see that the identity map induces identity maps, and that the composition of two cellular maps induces the composition of induced maps. Theorem 3.41 is best when one uses the alternative definition of cellular homology using the relative homology groups. It will follow in that context from the naturality of the associated long exact sequence of a pair. We postpone the precise argument until Subsection 5.2.2. 

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