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The target genes in the Notch pathway are expressed by a variety of translocation, post-translational modifications and activation of ligands associated to it. Following translation, Furin-like convertase modifies the ''Notch'' receptor by proteolytic cleavage at site 1 (S1)and transported to the cell surface held together by the heterodimerization (HD) domain. The ''Notch'' receptor on the signal‐receiving cell binds to a ligand on the cell surface of a neighboring signal‐sending cell, causing it to get activated. This binding causes a change in the conformation of the receptor. Site 2 (S2), present within the negative regulatory region (NRR) domain, is thus exposed for cleavage by a disintegrin and metalloprotease (ADAM). Notch cleavage at S2 generates the membrane‐anchored Notch extracellular truncation (NEXT) fragment, a substrate for the γ‐secretase complex. Thus, the ''Notch'' receptor is cleaved by the γ-secretase complex. Following γ-secretase cleavage, the intracellular domain (ICD) of Notch translocates to the nucleus where it interacts with the DNA-binding factor RBPJ and co-activators of the mastermind-like (MAML) family to form a transcriptional activation complex. <ref>doi:10.1634/theoncologist.2017-0677</ref>
The target genes in the Notch pathway are expressed by a variety of translocation, post-translational modifications and activation of ligands associated to it. Following translation, Furin-like convertase modifies the ''Notch'' receptor by proteolytic cleavage at site 1 (S1)and transported to the cell surface held together by the heterodimerization (HD) domain. The ''Notch'' receptor on the signal‐receiving cell binds to a ligand on the cell surface of a neighboring signal‐sending cell, causing it to get activated. This binding causes a change in the conformation of the receptor. Site 2 (S2), present within the negative regulatory region (NRR) domain, is thus exposed for cleavage by a disintegrin and metalloprotease (ADAM). Notch cleavage at S2 generates the membrane‐anchored Notch extracellular truncation (NEXT) fragment, a substrate for the γ‐secretase complex. Thus, the ''Notch'' receptor is cleaved by the γ-secretase complex. Following γ-secretase cleavage, the intracellular domain (ICD) of Notch translocates to the nucleus where it interacts with the DNA-binding factor RBPJ and co-activators of the mastermind-like (MAML) family to form a transcriptional activation complex. <ref>doi:10.1634/theoncologist.2017-0677</ref>


NRR mutations act by destabilizing or completely unfolding the HD domain, relaxing the interface that protects the S2 site.  These mutations associated with the HD domain in the NRR domain lead to increased Notch signaling by way increased expression of the target gene that leads to abnormal levels of the ICD of Notch. These abnormally high levels of ICD of the Notch receptors are understood to be the cause of the development of several different human cancers.
NRR mutations act by destabilizing or completely unfolding the HD domain, relaxing the interface that protects the S2 site.  These mutations associated with the HD domain in the NRR domain lead to increased Notch signaling by way increased expression of the target gene that leads to abnormal levels of the ICD of Notch. These abnormally high levels of ICD of the Notch receptors are understood to be the cause of the development of several different human cancers.<ref name="oncogene">Bernasconi-Elias, P., Hu, T., Jenkins, D. et al. Characterization of activating mutations of NOTCH3 in T-cell acute lymphoblastic leukemia and anti-leukemic activity of NOTCH3 inhibitory antibodies. Oncogene 35, 6077–6086 (2016). https://doi.org/10.1038/onc.2016.133</ref> Activating mutations of two different regions of NOTCH1 were present in >50% of T-cell acute lymphoblastic leukemia (T-ALL). Abnormally high amounts of NOTCH3 were reported to be in approximately 10–25% of ovarian adenocarcinomas. NOTCH3 mutations have also been reported in around 1% of head and neck squamous carcinomas, ovarian cancers, and lung adenocarcinoma. <ref name="oncogene" />
Activating mutations of two different regions of NOTCH1 were present in >50% of T-cell acute lymphoblastic leukemia (T-ALL). Abnormally high amounts of NOTCH3 were reported to be in approximately 10–25% of ovarian adenocarcinomas. NOTCH3 mutations have also been reported in around 1% of head and neck squamous carcinomas, ovarian cancers, and lung adenocarcinoma. <ref>Bernasconi-Elias, P., Hu, T., Jenkins, D. et al. Characterization of activating mutations of NOTCH3 in T-cell acute lymphoblastic leukemia and anti-leukemic activity of NOTCH3 inhibitory antibodies. Oncogene 35, 6077–6086 (2016). https://doi.org/10.1038/onc.2016.133</ref>


== Relevance ==
== Relevance ==

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