A putative cap binding protein and the methyl phosphate capping enzyme Bin3/MePCE function in telomerase biogenesis

Diego J Páez-Moscoso,Laurence Florens,David V Ho,Lili Pan,Katie Hildebrand,Peter Baumann,Michaella J Levy,Kristi L Jensen

doi:10.1038/s41467-022-28545-9

Abstract

Telomerase reverse transcriptase (TERT) and the noncoding telomerase RNA (TR) subunit constitute the core of telomerase. Additional subunits are required for ribonucleoprotein complex assembly and in some cases remain stably associated with the active holoenzyme. Pof8, a member of the LARP7 protein family is such a constitutive component of telomerase in fission yeast. Using affinity purification of Pof8, we have identified two previously uncharacterized proteins that form a complex with Pof8 and participate in telomerase biogenesis. Both proteins participate in ribonucleoprotein complex assembly and are required for wildtype telomerase activity and telomere length maintenance. One factor we named Thc1 (Telomerase Holoenzyme Component 1) shares structural similarity with the nuclear cap binding complex and the poly-adenosine ribonuclease (PARN), the other is the ortholog of the methyl phosphate capping enzyme (Bin3/MePCE) in metazoans and was named Bmc1 (Bin3/MePCE 1) to reflect its evolutionary roots. Thc1 and Bmc1 function together with Pof8 in recognizing correctly folded telomerase RNA and promoting the recruitment of the Lsm2-8 complex and the catalytic subunit to assemble functional telomerase.

Highlights

Telomerase reverse transcriptase (TERT) and the noncoding telomerase RNA (TR) subunit constitute the core of telomerase
Telomerase is comprised of the catalytic protein Telomerase reverse transcriptase (TERT, Trt[1] in Schizosaccharomyces pombe), the telomerase RNA subunit (TR, TER1 in S. pombe), and an unknown number of other protein subunits involved in the biogenesis, regulation, and recruitment of the enzyme to telomeres
The samples were analyzed by multidimensional protein identification technology (MudPIT) and 19 proteins with an average distributed Normalized Spectral Abundance Factor of >0.005 in the tagged samples were found to be enriched in the Pof[8] immunoprecipitates (Supplementary Fig. 1b and Supplementary Table 1)

Summary

Introduction

Telomerase reverse transcriptase (TERT) and the noncoding telomerase RNA (TR) subunit constitute the core of telomerase. In S. pombe, the telomerase RNA subunit TER16,7 is transcribed by RNA polymerase II and the primary transcript contains two exons and an intron[8] This precursor is processed by the spliceosome. Deviating from a normal splicing reaction, the intermediates generated by the first spliceosomal cleavage reaction are released with the 5′ exon being further processed into mature telomerase RNA and the intron lariat-exon 2 being degraded. This “discard” of splicing intermediates[9] is promoted by RNA elements within TER1 that are unfavorable for a transition to the second step of splicing. RNA in other species, but the underlying mechanisms for releasing splicing intermediates as cleavage products are remarkably diverse[10,11]

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Results

Conclusion