The TOP2 gene of Trypanosoma brucei: a single-copy gene that shares extensive homology with other TOP2 genes encoding eukaryotic DNA topoisomerase II

Over 30 MAK (maintenance of killer) genes are necessary for propagation of the killer toxin-encoding M1 satellite double-stranded RNA of the L-A virus. Sequence analysis revealed that MAK7 is RPL4A, one of the two genes encoding ribosomal protein L4 of the 60S subunit. We further found that mutants with mutations in 18 MAK genes (including mak1 [top1], mak7 [rpl4A], mak8 [rpl3], mak11, and mak16) had decreased free 60S subunits. Mutants with another three mak mutations had half-mer polysomes, indicative of poor association of 60S and 40S subunits. The rest of the mak mutants, including the mak3 (N-acetyltransferase) mutant, showed a normal profile. The free 60S subunits, L-A copy number, and the amount of L-A coat protein in the mak1, mak7, mak11, and mak16 mutants were raised to the normal level by the respective normal single-copy gene. Our data suggest that most mak mutations affect M1 propagation by their effects on the supply of proteins from the L-A virus and that the translation of the non-poly(A) L-A mRNA depends critically on the amount of free 60S ribosomal subunits, probably because 60S association with the 40S subunit waiting at the initiator AUG is facilitated by the 3' poly(A).

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In vivo phosphorylation of the 170-kDa form of eukaryotic DNA topoisomerase II

Journal of Biological Chemistry ◽

10.1016/s0021-9258(19)84802-0 ◽

1989 ◽

Vol 264 (26) ◽

pp. 15161-15164 ◽

Cited By ~ 2

Author(s):

M M Heck ◽

W N Hittelman ◽

W C Earnshaw

Keyword(s):

Topoisomerase Ii ◽

Dna Topoisomerase Ii ◽

Dna Topoisomerase ◽

Eukaryotic Dna

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The Dynein Gene Family in Chlamydomonas reinhardtii

Genetics ◽

10.1093/genetics/144.2.569 ◽

1996 ◽

Vol 144 (2) ◽

pp. 569-585 ◽

Cited By ~ 3

Author(s):

Mary E Porter ◽

Julie A Knott ◽

Steven H Myster ◽

Samuel J Farlow

Keyword(s):

Gene Family ◽

Genetic Map ◽

Single Copy ◽

Amino Acid Sequences ◽

Single Copy Gene ◽

Heavy Chains ◽

Length Polymorphisms ◽

Copy Gene ◽

Genes Encoding ◽

Insight Into

Abstract To correlate dynein heavy chain (Dhc) genes with flagellar mutations and gain insight into the function of specific dynein isoforms, we placed eight members of the Dhc gene family on the genetic map of Chlamydomonas. Using a PCR-based strategy, we cloned 11 Dhc genes from Chlamydomonas. Comparisons with other Dhc genes indicate that two clones correspond to genes encoding the alpha and beta heavy chains of the outer dynein arm. Alignment of the predicted amino acid sequences spanning the nucleotide binding site indicates that the remaining nine clones can be subdivided into three groups that are likely to include representatives of the inner-arm Dhc isoforms. Gene-specific probes reveal that each clone represents a single-copy gene that is expressed as a transcript of the appropriate size (>13 kb) sufficient to encode a high molecular weight Dhc polypeptide. The expression of all nine genes is upregulated in response to deflagellation, suggesting a role in axoneme assembly or motility. Restriction fragment length polymorphisms between divergent C. reinhardtii strains have been used to place each Dhr gene on the genetic map of Chlamydomonas. These studies lay the groundwork for correlating defects in different Dhc genes with specific flagellar mutations.

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