Abstract
Heterogeneous nuclear ribonucleoproteins (hnRNPs) are structurally and functionally distinct proteins containing specific domains and motifs that enable the proteins to bind certain nucleotide sequences, particularly those found in human telomeres. In human malignant cells (HMCs), hnRNP-A1—the most studied hnRNP—is an abundant multifunctional protein that interacts with telomeric DNA and affects telomerase function. In addition, it is believed that other hnRNPs in HMCs may also be involved in the maintenance of telomere length. Accordingly, these proteins are considered possible participants in the processes associated with HMC immortalization. In our review, we discuss the results of studies on different hnRNPs that may be crucial to solving molecular oncological problems and relevant to further investigations of these proteins in HMCs.
Highlights
In 1971, Alexey Olovnikov hypothesized that with each cell division, the DNA at chromosomal ends is slightly shortened, and in some cells, this shortening eliminates a special enzyme
The different domains and motifs that determine the ability of Heterogeneous nuclear ribonucleoproteins (hnRNPs) to bind various nucleotide sequences are established
Special emphasis is placed on hnRNPs that contain RRM domains, which permit recognition of and binding to d(TTAGGG) repeats in a terminal 3 single-stranded overhang of telomeric DNA
Summary
In 1971, Alexey Olovnikov hypothesized that with each cell division, the DNA at chromosomal ends (telomeres) is slightly shortened, and in some (cancer) cells, this shortening eliminates a special enzyme (called telomerase). The identified structural and functional features of hnRNPs, especially the presence of different RNA-binding domains, have resulted in these proteins being grouped often into a special class that consists of several protein families, subfamilies, and individual members (see below). The hnRNP-A1A and A1-B isoforms are very similar in structure (Figure 2); for example, the N-terminal ends of these proteins with functionally important RRM domains are identical [P09651 UniProt]. Since the protein products of different genes, as well as proteoforms, can vary significantly in their properties (including their ability to interact with telomeres), it is important to assign an individual designation to each such product to prevent confusion and ambiguity when interpreting experimental results ( those obtained from studying HMCs)
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