The activity of CobB1 protein deacetylase contributes to nucleoid compaction in Streptomyces venezuelae spores by increasing HupS affinity for DNA.

Streptomyces are soil bacteria with complex life cycle. During sporulation Streptomyces linear chromosomes become highly compacted so that the genetic material fits within limited spore volume. The key players in this process are nucleoid-associated proteins (NAPs). Among them, HU (heat unstable) proteins are the most abundant NAPs in the cell and the most conserved in bacteria. HupS, one of the two HU homologues encoded by the Streptomyces genome, is the best-studied spore-associated NAP. In contrast to other HU homologues, HupS contains a long, C-terminal domain that is extremely rich in lysine repeats (LR domain) similar to eukaryotic histone H2B and mycobacterial HupB protein. Here, we have investigated, whether lysine residues in HupS are posttranslationally modified by reversible lysine acetylation. We have confirmed that Streptomyces venezuelae HupS is acetylated in vivo. We showed that HupS binding to DNA in vitro is controlled by the acetylation. Moreover, we identified that CobB1, one of two Sir2 homologues in Streptomyces, controls HupS acetylation levels in vivo. We demonstrate that the elimination of CobB1 increases HupS mobility, reduces chromosome compaction in spores, and affects spores maturation. Thus, our studies indicate that HupS acetylation affects its function by diminishing DNA binding and disturbing chromosome organization.

Spatial rearrangement of the Streptomyces venezuelae linear chromosome during sporogenic development.

Bacteria of the genus Streptomyces have a linear chromosome, with a core region and two 'arms'. During their complex life cycle, these bacteria develop multi-genomic hyphae that differentiate into chains of exospores that carry a single copy of the genome. Sporulation-associated cell division requires chromosome segregation and compaction. Here, we show that the arms of Streptomyces venezuelae chromosomes are spatially separated at entry to sporulation, but during sporogenic cell division they are closely aligned with the core region. Arm proximity is imposed by segregation protein ParB and condensin SMC. Moreover, the chromosomal terminal regions are organized into distinct domains by the Streptomyces-specific HU-family protein HupS. Thus, as seen in eukaryotes, there is substantial chromosomal remodelling during the Streptomyces life cycle, with the chromosome undergoing rearrangements from an 'open' to a 'closed' conformation.

Transthoracic echocardiography in the assessment of cardiogenic causes of ischaemic stroke.

INTRODUCTION: One of the leading causes of death in Poland is stroke. Cardiogenic stroke is known to be one of the most important reasons for acute ischaemic stroke (AIS), comprising 25-30% of all AISs. AIM OF STUDY: Assessment of the prevalence of different risk factors of cardiogenic causes of AIS using transthoracic echocardiography (TTE). MATERIAL AND METHODS: Transthoracic echocardiograms performed in patients with AIS admitted to a single neurological ward between October 2013 and September 2017 were analysed. Patients were assigned, based on the results of their TTE and their previous medical history of atrial fibrillation (AF), to one of three groups depending on the level of the risk of occurrence of cardiogenic causes of AIS. ETHICAL PERMISSION: According to Dz.U.2001, no. 126, 1381 no ethical permission was needed. RESULTS: 663 patients with AIS were included in the study. Patients with high risk of cardiogenic cause of AIS: 26.7% (N = 177 patients [p]). Of these, 64.4% (114 p) were diagnosed with AF. 31.6% (56 p) with sinus rhythm during hospitalisation had a history of paroxysmal AF (PAF). In 11.9% (21 p) of the patients qualified to the high risk group, factors other than AF were found. Patients with moderate risk of cardiogenic cause of AIS: 10.1% (67 p). Patients with low risk of cardiogenic cause of AIS: 25.9% (172 p). Echocardiographic results led to a change in therapy in 1.21% of cases. CONCLUSIONS: 1. Transthoracic echocardiography performed routinely in all AIS patients affects the treatment in a very low percentage of cases. 2. The group that could benefit the most from TTE examination includes people without established indications for chronic anticoagulant therapy, in particular patients after myocardial infarction and people with additional clinical symptoms. 3. In patients with AIS, the diagnostic sensitivity of TTE in the detection of PFO is low. Young people with a cryptogenic ischaemic stroke should undergo a transoesophageal assessment.