Malignant Ileocolocolic Intussusception in a 19-Year-Old Male.

Adult intussusception is an infrequent occurrence typically resulting from an identifiable lead point of a benign or malignant etiology. Here, we present a case of a 19-year-old male who presented to the emergency department with complaints of abdominal pain, intractable nausea, and fluctuations between bloody diarrhea and constipation. These symptoms had begun two months prior and had increased in severity, resulting in significant appetite changes.

Guanine-containing ssDNA and RNA induce dimeric and tetrameric structural forms of SAMHD1.

The dNTPase activity of tetrameric SAM and HD domain containing deoxynucleoside triphosphate triphosphohydrolase 1 (SAMHD1) plays a critical role in cellular dNTP regulation. SAMHD1 also associates with stalled DNA replication forks, DNA repair foci, ssRNA and telomeres. The above functions require nucleic acid binding by SAMHD1, which may be modulated by its oligomeric state.

Guanine-containing ssDNA and RNA induce dimeric and tetrameric SAMHD1 in cryo-EM and binding studies.

The dNTPase activity of tetrameric SAM and HD domain containing deoxynucleoside triphosphate triphosphohydrolase 1 (SAMHD1) plays a critical role in cellular dNTP regulation. SAMHD1 also associates with stalled DNA replication forks, DNA repair foci, ssRNA, and telomeres. The above functions require nucleic acid binding by SAMHD1, which may be modulated by its oligomeric state.

Deoxyguanosine-Linked Bifunctional Inhibitor of SAMHD1 dNTPase Activity and Nucleic Acid Binding.

Sterile alpha motif histidine-aspartate domain protein 1 (SAMHD1) is a deoxynucleotide triphosphohydrolase that exists in monomeric, dimeric, and tetrameric forms. It is activated by GTP binding to an A1 allosteric site on each monomer subunit, which induces dimerization, a prerequisite for dNTP-induced tetramerization. SAMHD1 is a validated drug target stemming from its inactivation of many anticancer nucleoside drugs leading to drug resistance.