#RNA modification

Processing of rRNA and tRNA

Pseudouridine differs from uridine by

Pseudouridine, the most abundant RNA modification, is a C5-glycoside isomer of uridine. Normal uridine uses an N1-C1' nitrogen-carbon glycosidic linkage between base and ribose. During pseudouridylation by pseudouridine synthases, the uracil ring rotates, creating a C5-C1' carbon-carbon bond, retaining Watson-Crick face but exposing N1-H as additional hydrogen-bond donor. This C-C linkage increases base stacking, backbone rigidity via water-mediated interactions, thermal stability, and improves translational fidelity in tRNA and rRNA. It occurs post-transcriptionally in nucleolus and is conser

Ref: Alberts et al., Molecular Biology of the Cell, 7th ed., Chapter 6, RNA Modifications, Pseudouridine C-C glycosidic bond formation

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Processing of mRNA, rRNA, tRNA

Box H/ACA snoRNAs guide

Box H/ACA small nucleolar RNAs contain two hairpin structures linked by H box ANANNA and terminated by ACA box three nucleotides from three prime end, forming hairpin-hinge-hairpin-tail architecture. Each hairpin harbors internal pseudouridylation pocket with antisense elements flanking target uridine left unpaired for isomerization. Core proteins include pseudouridine synthase dyskerin Cbf5, NOP10, Nhp2, Gar1. Dyskerin isomerizes uridine to pseudouridine via base rotation adding extra NH hydrogen donor strengthening base stacking and water-mediated interactions, enhancing ribosome stability.

Ref: Lodish et al., Molecular Cell Biology, 9th ed., Chapter 11: Box H/ACA guides pseudouridylation; Alberts 7th ed., Pseudouridine synthase function

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Processing of mRNA, rRNA, tRNA

Box C/D snoRNAs guide

Box C/D small nucleolar RNAs are defined by conserved motifs Box C RUGAUGA and Box D CUGA near five prime and three prime ends that fold into kink-turn structures bound by core proteins Snu13, NOP56, NOP58, and methyltransferase fibrillarin Nop1. Each snoRNA contains antisense guide element ten to twenty-one nucleotides complementary to pre-ribosomal RNA placing target ribose five nucleotides upstream of Box D or D' for methylation. Reaction transfers methyl group from SAM to 2'-hydroxyl creating 2'-O-methyl ribose enhancing hydrophobic stacking and nuclease resistance concentrated within func

Ref: Lodish et al., Molecular Cell Biology, 9th ed., Chapter 11: Box C/D snoRNAs guide methylation; Alberts 7th ed., snoRNP mediated methylation

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DNA

Which molecule contains N6-methyladenosine as a minor base?

Bacterial DNA accurately describes the structural composition or molecular organization asked about in this question. In Nucleic Acid, knowledge of molecular structure is directly linked to understanding biological function. The specific arrangement of chemical components in Bacterial DNA determines its physical properties, biological activity, and interactions with other molecules. The other options (tRNA, mRNA, and Ribosomal RNA) describe different structural arrangements, incorrect stoichiometry, or compositions of different biological molecules.

Ref: Campbell Biology, Urry et al., 12th Ed.

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