Biology subjects

Heim, A.

Publications and source records attributed to Heim, A..

3 recordsLinked to original sources

bioRxiv2022

Cyclin B3 implements timely vertebrate oocyte arrest for fertilization

To ensure successful offspring ploidy, vertebrate oocytes must halt the cell cycle in meiosis II until sperm entry. Emi2 is essential to keep oocytes arrested until fertilization. Yet, how this arrest is implemented exclusively in meiosis II and not prematurely in meiosis I remained enigmatic. Using mouse and frog oocytes, we show here that cyclin B3, an understudied B- type cyclin, is essential to keep Emi2 levels low in meiosis I. Direct phosphorylation of Emi2 at an evolutionarily highly conserved site by Cdk1/cyclin B3 targets Emi2 for degradation. In contrast, Cdk1/cyclin B1 is inefficient in Emi2 phosphorylation providing a molecular explanation for the requirement of different B-type cyclins for oocyte maturation. Cyclin B3 degradation at exit from meiosis I enables Emi2 accumulation and thus, timely arrest in meiosis II. Our findings illuminate the evolutionarily conserved mechanisms controlling oocyte arrest for fertilization at the correct cell cycle stage, essential for embryo viability.

cell biology↗

bioRxiv2022

Molecular Phylogeny of human adenovirus type 41 lineages

Type 41 of human adenovirus species F (HAdV-F41) is a frequent aetiology of gastroenteritis in children, and nosocomial as well as kindergarten outbreaks have been frequently described. In contrast to other HAdV types, HAdV-F41 was not associated with life-threatening disseminated disease in allogeneic haematopoietic stem cell transplant (HSCT) recipients or any severe organ infections so far. Due to the limited clinical significance, the evolution of HAdV-F41 has not been studied in detail. Recently, HAdV-F41 has been associated with severe hepatitis in young children, and interest in HAdV-F41 has skyrocketed, although the aetiology of the hepatitis has not been resolved. Complete genomic HAdV-F41 sequences from 32 diagnostic specimens of the past 11 years (2011-2022) were generated, all originating from gastroenteritis patients. Additionally, 33 complete HAdV-F41 genomes from GenBank were added to our phylogenetic analysis. Phylogenetic analysis of 65 genomes indicated that HAdV-F41 evolved with three lineages co-circulating. Lineage 1 included the prototype Tak from 1973 and six isolates from 2007 to 2017 with an average nucleotide identity of 99.3 %. Lineage 2 included 53 isolates from 2000 to 2022, had an average nucleotide identity of 99.8 %, and split into two sublineages. Lineage 3, probably described for the first time in 2009, had a 45nt deletion in the long fiber gene and had evolved significantly in the short fiber and E3 region. Moreover, a recent lineage 3 isolate from 2022 had a recombinant phylogeny of the short fiber gene. Fibers interact with cellular receptors and determine cellular tropism, whereas E3 gene products interfere with the immune recognition of HAdV infected cells. This in-depth study on the phylogeny of HAdV-F41 discovered significant evolution of recently described lineage 3 of HAdV-F41, possibly resulting in altered cellular tropism, virulence and pathophysiology.

microbiology↗

bioRxiv2020

The zinc finger antiviral protein ZAP destabilises viral transcripts and restricts cytomegalovirus

Interferon-stimulated gene products (ISGs) play a crucial role in early infection control. The ISG zinc finger CCCH-type antiviral protein 1 (ZAP/ZC3HAV1) antagonises several RNA viruses by binding to CG-rich RNA sequences, whereas its effect on DNA viruses is largely unknown. Here, we decipher the role of ZAP in the context of human cytomegalovirus (HCMV) infection, a {beta}-herpesvirus that is associated with high morbidity in immunosuppressed individuals and newborns. We show that expression of the two major isoforms of ZAP, the long (ZAP-L) and short (ZAP-S), is induced during HCMV infection and that both negatively affect HCMV replication. Transcriptome and proteome analyses demonstrated that the expression of ZAP decelerates the progression of HCMV infection. SLAM-sequencing revealed that ZAP restricts HCMV at early stages of infection by destabilising a distinct subset of viral transcripts with low CG content. In summary, this report provides evidence of an important antiviral role for ZAP in host defense against HCMV infection and highlights its differentiated function during DNA virus infection.

molecular biology↗